VSI TCP/IP Services for OpenVMS Tuning and Troubleshooting
- Operating System and Version:
- VSI OpenVMS IA-64 Version 8.4-1H1 or higher
VSI OpenVMS Alpha Version 8.4-2L1 or higher
Preface
The VSI TCP/IP Services for OpenVMS product is the VSI implementation of the TCP/IP networking protocol suite and internet services for VSI OpenVMS Alpha and VSI OpenVMS VAX systems.
TCP/IP Services provides a comprehensive suite of functions and applications that support industry-standard protocols for heterogeneous network communications and resource sharing.
This manual provides system and network managers with information they need to identify and resolve problems. This manual is best used in conjunction with the VSI TCP/IP Services for OpenVMS Management manual.
See the VSI TCP/IP Services for OpenVMS Installation and Configuration manual for information about installing, configuring, and starting this product.
1. About VSI
VMS Software, Inc. (VSI) is an independent software company licensed by Hewlett Packard Enterprise to develop and support the OpenVMS operating system.
2. Intended Audience
This manual is for OpenVMS or UNIX system managers who are experienced in troubleshooting complex software products. This manual assumes a working knowledge of TCP/IP networking, TCP/IP terminology, and familiarity with TCP/IP Services. Always read all the current product documentation before attempting to resolve any problems.
3. Document Structure
Chapter 1 describes how to determine the cause of networking problems. It introduces some tools useful in monitoring and diagnosing these problems.
Chapter 2 describes the TCP/IP subsystem attributes that you can adjust to improve network performance.
Appendix A describes the tools available for isolating and resolving network problems.
4. Related Documents
Table 1 lists the documents available with this version of TCP/IP Services.
|
Manual |
Contents |
|---|---|
|
VSI TCP/IP Services for OpenVMS Concepts and Planning |
This manual provides conceptual information about TCP/IP networking on OpenVMS systems, including general planning issues to consider before configuring your system to use the TCP/IP Services software. This manual also describes the manuals in the TCP/IP Services documentation set and provides a glossary of terms and acronyms for the TCP/IP Services software product. |
|
VSI TCP/IP Services for OpenVMS Release Notes |
The release notes provide version-specific information that supersedes the information in the documentation set. The features, restrictions, and corrections in this version of the software are described in the release notes. Always read the release notes before installing the software. |
|
VSI TCP/IP Services for OpenVMS Installation and Configuration |
This manual explains how to install and configure the TCP/IP Services product. |
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VSI TCP/IP Services for OpenVMS User's Guide |
This manual describes how to use the applications available with TCP/IP Services such as remote file operations, email, TELNET,TN3270, and network printing. |
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VSI TCP/IP Services for OpenVMS Management |
This manual describes how to configure and manage the TCP/IP Services product. |
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VSI TCP/IP Services for OpenVMS Management Command Reference |
This manual describes the TCP/IP Services management commands. |
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VSI TCP/IP Services for OpenVMS Management Command Quick Reference Card |
This reference card lists the TCP/IP management commands by component and describes the purpose of each command. |
|
VSI TCP/IP Services for OpenVMS UNIX Command Equivalents Reference Card |
This reference card contains information about commonly performed network management tasks and their corresponding TCP/IP management and Tru64 UNIX command formats. |
|
VSI TCP/IP Services for OpenVMS ONC RPC Programming |
This manual presents an overview of high-level programming using open network computing remote procedure calls (ONCRPCs). This manual also describes the RPC programming interface and how to use the RPCGEN protocol compiler to create applications. |
|
VSI TCP/IP Services for OpenVMS Sockets API and System Services Programming |
This manual describes how to use the Sockets API and OpenVMS system services to develop network applications. |
|
VSI TCP/IP Services for OpenVMS SNMP Programming and Reference |
This manual describes the Simple Network Management Protocol (SNMP) and the SNMP application programming interface (eSNMP). It describes the subagents provided with TCP/IP Services, utilities provided for managing subagents, and how to build your own subagents. |
|
VSI TCP/IP Services for OpenVMS Tuning and Troubleshooting |
This manual provides information about how to isolate the causes of network problems and how to tune the VSI TCP/IP Services software for the best performance. |
|
VSI TCP/IP Services for OpenVMS Guide to IPv6 |
This manual describes the IPv6 environment, the roles of systems in this environment, the types and function of the different IPv6 addresses, and how to configure TCP/IP Services to access the IPv6 network. |
For additional information about VSI OpenVMS products and services, see the website:
5. OpenVMS Documentation
The full VSI OpenVMS documentation set can be found on the VMS Software Documentation webpage at https://docs.vmssoftware.com.
6. VSI Encourages Your Comments
You may send comments or suggestions regarding this manual or any VSI document by sending electronic mail to the following Internet address: <docinfo@vmssoftware.com>. Users who have VSI OpenVMS support contracts through VSI can contact <support@vmssoftware.com> for help with this product.
7. Conventions
VSI TCP/IP Services for OpenVMS Alpha
VSI TCP/IP Services for OpenVMS VAX
In addition, please note that all IP addresses are fictitious.
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Ctrl/x |
A sequence such as Ctrl/x indicates that you must hold down the key labeled Ctrl while you press another key or a pointing device button. |
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PF1 x |
A sequence such as PF1 x indicates that you must first press and release the key labeled PF1 and then press and release another key or a pointing device button. |
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Return |
In examples, a key name enclosed in a box indicates that you press a key on the keyboard. (In text, a key name is not enclosed in a box.) In the HTML version of this document, this convention appears as brackets, rather than a box. |
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… |
A horizontal ellipsis in examples indicates one of the
following possibilities:
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A vertical ellipsis indicates the omission of items from a code example or command format; the items are omitted because they are not important to the topic being discussed. |
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( ) |
In command format descriptions, parentheses indicate that you must enclose choices in parentheses if you specify more than one. |
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[ ] |
In command format descriptions, brackets indicate optional choices. You can choose one or more items or no items. Do not type the brackets on the command line. However, you must include the brackets in the syntax for OpenVMS directory specifications and for a substring specification in an assignment statement. |
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In command format descriptions, vertical bars separate choices within brackets or braces. Within brackets, the choices are optional; within braces, at least one choice is required. Do not type the vertical bars on the command line. |
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{ } |
In command format descriptions, braces indicate required choices; you must choose at least one of the items listed. Do not type the braces on the command line. |
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bold type |
This typeface represents the introduction of a new term. It also represents the name of an argument, an attribute, or a reason. |
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italic type |
Italic text indicates important information, complete titles of manuals, or variables. Variables include information that varies in system output (Internal error number),in command lines (/PRODUCER=name), and in command parameters in text (where dd represents the predefined code for the device type). |
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UPPERCASE TEXT |
Uppercase text indicates a command, the name of a routine, the name of a file, or the abbreviation for a system privilege. |
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Monospace type indicates code examples and interactive screen displays. This typeface indicates UNIX system output or user input,commands, options, files, directories, utilities, hosts, and users. In the C programming language, this typeface identifies the following elements: keywords, the names of independently compiled external functions and files, syntax summaries, and references to variables or identifiers introduced in an example. |
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- |
A hyphen at the end of a command format description, command line, or code line indicates that the command or statement continues on the following line. |
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numbers |
All numbers in text are assumed to be decimal unless otherwise noted. Nondecimal radixes—binary, octal, or hexadecimal—are explicitly indicated. |
Chapter 1. Troubleshooting Techniques and Tools
This chapter provides information that helps you identify symptoms, isolate problems, and take steps to resolve your network problem. This chapter also introduces the tools available to help you monitor and diagnose problems with your network software, devices, and interfaces.
1.1. Using Symptoms to Identify a Problem
1.2. Isolating Problems
$ SHOW DEVICE BG Device Device Error Name Status Count BG0: Mounted 0 BG5: Mounted 0 BG6: Mounted 0 BG7: Mounted 0 BG8: Mounted 0 . . .
If the command output shows only the BG0: device, then the product is stopped.
Does the problem occur all the time or intermittently?
Does it involve all hosts or is it limited to one host?
Are there special load or configuration conditions under which you encounter a specific problem?
Does the problem affect a single user? Multiple users? Your LAN?
Check connectivity. (Section 1.2.1)
Check network interface parameters. (Section 1.2.2)
Check the IP address to Ethernet address translation tables. (Section 1.2.3)
Examine network statistics. (Section 1.2.4)
Monitor network traffic. (Section 1.2.5)
Check name server operation. (Section 1.2.7)
Check the route to a remote host. (Section 1.2.8)
Check the routes known to a gateway. (Section 1.2.9)
Check whether the network services have been enabled. (Section 1.2.10)
Look for application errors or interoperability issues.
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Diagnostic Tool |
Function |
|---|---|
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Controls and displays ARP tables. |
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Sends domain name query packets to name servers. |
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Configures or displays network interface parameters, redefines an address for a particular interface, or sets options such as an alias list, broadcast address, or access filter. Use to detect incorrect IP addresses, subnet masks, and broadcast addresses. |
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Allows the name server administrator to send messages to a name server to start, stop, and restart BIND; to dump the BIND database; to check the status of the BIND process; and to change the tracing level. |
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Displays network statistics of sockets, data link counters, specified protocols or aliases, network interfaces, and a host's routing table. |
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Provides the ability to directly query a name server and retrieve information. Use NSLOOKUP to determine whether your local name server is running correctly or to retrieve information from remote name servers. |
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Indicates a host is reachable, and displays statistics about packet loss and delivery time. |
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Allows the user to manipulate the network routing tables manually. |
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Displays and maintains the various network subsystem attributes. |
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Traces packets going in and out of the system. To run the trace utility, enter the DCL command TCPTRACE. |
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Displays the route of an IP packet sent from the local host to a remote host. |
To enter a command at the system prompt, first run the SYS$STARTUP:TCPIP$DEFINE_COMMANDS.COM procedure. This procedure defines each tool as a foreign command.
See Appendix A for complete reference information about these diagnostic tools.
1.2.1. Testing Connectivity Between Network Hosts
Use the ping command to test whether you can reach a remote host from
your local system. The ping command sends an Internet Control Message
Protocol (ICMP) echo request to the specified host name or host address. When
received by a host, an ICMP reply is returned to the requester.
ping command to isolate a problem, you should first
test the localhost to verify that the system can communicate with
itself. For
example:TCPIP> ping localhost PING LOCALHOST (127.0.0.1): 56 data bytes 64 bytes from 127.0.0.1: icmp_seq=0 ttl=64 time=1 ms 64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=1 ms 64 bytes from 127.0.0.1: icmp_seq=2 ttl=64 time=0 ms 64 bytes from 127.0.0.1: icmp_seq=3 ttl=64 time=0 ms ----LOCALHOST PING Statistics---- 4 packets transmitted, 4 packets received, 0% packet loss round-trip (ms) min/avg/max = 0/0/1 ms TCPIP> TCPIP> ping 127.0.0.1 PING 127.0.0.1 (127.0.0.1): 56 data bytes 64 bytes from 127.0.0.1: icmp_seq=0 ttl=64 time=1 ms 64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=1 ms 64 bytes from 127.0.0.1: icmp_seq=2 ttl=64 time=0 ms 64 bytes from 127.0.0.1: icmp_seq=3 ttl=64 time=0 ms ----127.0.0.1 PING Statistics---- 4 packets transmitted, 4 packets received, 0% packet loss round-trip (ms) min/avg/max = 0/0/1 ms
The output from this ping command shows that the system is able to
send a message down and then back up the protocol stack through the loopback
address. The host address 127.0.0.1 and its associated host name,
localhost, are the loopback address of the local host. This address
was devised so that software could use common code to address local processes as
well as remote processes. If the command output shows that it received a message for
every message it transmitted, then you can be sure that the network software is up
and running and that your system should able to communicate with remote
systems.
VSI TCP/IP Services may not be running.
A definition for
localhostis missing from the local database.
If the ping command for localhost does not respond
correctly, try the ping command with the IP address
127.0.0.1. If this command displays correct output, the TCPIP
database is missing a definition for localhost.
If localhost returns the data correctly at this point, use the
ping command to test another host on the same local network. If you
are able to reach this host, then test remote hosts farther and farther away from
the local host.
ping command
displays the following message:
TCPIP> ping a7u1kt ping: unknown host a7u1kt %SYSTEM-F-UNREACHABLE, remote node is not currently reachable
ping command, the output may
be:TCPIP> ping 10.10.22.1 PING 10.10.22.1 (10.10.22.1): 56 data bytes ----10.10.22.1 PING Statistics---- 4 packets transmitted, 0 packets received, 100% packet loss %SYSTEM-F-TIMEOUT, device timeout
There is no host with the specified host name.
Using the host file or DNS/BIND, the system was not able to resolve the specified host name to an IP address.
There is no host with that IP address.
The host is down and not responding.
ping statistics
displayed:TCPIP> ping chester PING chester (16.20.208.53): 56 data bytes 64 bytes from 16.20.208.53: icmp_seq=0 ttl=64 time=0 ms 64 bytes from 16.20.208.53: icmp_seq=1 ttl=64 time=1 ms 64 bytes from 16.20.208.53: icmp_seq=2 ttl=64 time=0 ms 64 bytes from 16.20.208.53: icmp_seq=3 ttl=64 time=1 ms ----chester PING Statistics---- 4 packets transmitted, 4 packets received, 0% packet loss round-trip (ms) min/avg/max = 0/0/1 ms
The ping command displays statistics on packets sent; packets
received; the percentage of packets lost; and the minimum, average, and maximum
round-trip packet times.
If you do not specify command options, the ping command displays the
results of each ICMP request in sequence, the number of bytes received from the
remote host, and the round-trip time on a per-request basis.
Use the output from the ping command to help determine the cause of
direct and indirect routing problems such as host is unreachable, connection timed
out, and network is unreachable.
This command helps you decide whether further testing is required and where. For
example, if someone reports a problem connecting to a remote host, but
ping shows packets traveling to the remote system and back, the
problem probably resides in the upper (application) layer protocols (such as FTP,
TELNET), or the user introduced the error to the application.
If the packets do not make the round trip, the problem probably resides in the lower layers, and perhaps indicates a misconfigured interface or other configuration or routing problems.
When preliminary testing indicates a problem in the lower layers, the next step is
to test the network interfaces and routing. Use the ifconfig,
netstat, and arp commands for these purposes (see
Appendix A).
1.2.1.1. Using ping on a Multihomed Host
The
pingcommand on another system topingthe IP address of the suspect interface. Because VSI TCP/IP Services sends messages via the first matching entry in the routing table, you might not be exercising the interface if you test on the local system.The
traceroute -s src_addrcommand on the local system. This command uses the IP address specified with the-sflag in outgoing probe packets. If the command fails, the error message may indicate that the problem is with the interface.
1.2.2. Checking the Network Interface Parameters
Use the ifconfig command to check the configuration of a network
interface. A common problem is a misconfigured subnet mask or incorrect IP address.
Be sure to check the values of these parameters.
TCPIP> ifconfig -a
LO0: flags=100c89<UP,LOOPBACK,NOARP,MULTICAST,SIMPLEX,NOCHECKSUM>
inet6 ::1
TN0: flags=80<NOARP>
WF0: flags=c43<UP,BROADCAST,RUNNING,MULTICAST,SIMPLEX>
*inet 10.10.2.1 netmask ffffff00 broadcast 10.10.2.255 ipmtu 1500
inet6 fe80::200:f8ff:febd:bc22
inet6 3ffe:1200:4120:1000:200:f8ff:febd:bc22TCPIP> ifconfig WF0
WF0: flags=c43<UP,BROADCAST,RUNNING,MULTICAST,SIMPLEX>
inet 127.0.0.1 netmask ffff0000 broadcast 10.10.2.255 ipmtu 4470
inet6 fe80::200:f8ff:febd:bc22
inet6 3ffe:1200:4120:1000:200:f8ff:febd:bc22The first line of this display shows the interface characteristics. The interface should be UP and RUNNING (exceptions to this are the LO0 and TN0 interfaces). The pertinent fields in this display show the interface's IP address, the subnet mask, the broadcast mask, and the maximum transmit unit.
TCPIP> SHOW INTERFACE
Packets
Interface IP_Addr Network mask Receive Send MTU
LO0 127.0.0.1 255.0.0.0 137 137 4096
WE0 10.10.2.1 255.255.255.0 5089 4191 1500
TCPIP> SHOW CONFIGURATION INTERFACE
Interface: LO0
IP_Addr: 127.0.0.1 NETWRK: 255.0.0.0 BRDCST:
Interface: WE0
IP_Addr: 10.10.2.1 NETWRK: 255.255.255.0 BRDCST: 10.10.2.255If you are not familiar with IP addressing and the concepts of subnet and broadcast masks, review the information in VSI TCP/IP Services for OpenVMS Management before proceeding with troubleshooting tasks.
1.2.3. Displaying and Modifying the Internet-to-Ethernet Translation Tables
Use the
arp utility or the SHOW ARP management command to check the IP
address to Ethernet address translation entries in the Address Resolution Protocol
(ARP) table. This is useful if you think incorrect entries are being added to the
ARP table. For example, if you enter a command and an unexpected host responds, you
may have two systems defined with the same IP address in the ARP table.
$ TCPIP SHOW ARP Cnt Flags Timer Host Phys Addr 1: UCS 451 160.20.0.10 08-00-2b-39-c7-ac 2: UC 0 160.20.0.100 aa-00-04-00-8d-13 3: UC 3 160.20.0.173 00-00-f8-45-a0-b4 4: UC 14 160.20.32.94 00-00-f8-00-f7-41 5: UC 50 160.20.64.69 00-d0-b7-19-78-a4 6: UCS 9 160.20.64.132 00-50-8b-72-7f-ff 7: UCS 150 160.20.80.124 00-50-8b-4d-91-b3
SET ARP allows you to add the hardware address to the ARP table.
SET PROTOCOL ARP allows you specify the time interval for ARP to hold information in its cache. Use the SET CONFIGURATION PROTOCOL ARP command to set this information in the permanent configuration database.
For more information about these commands, refer to the VSI TCP/IP Services for OpenVMS Management Command Quick Reference Card manual.
For information about using the arp utility, refer to Appendix A.
1.2.4. Examining Network Statistics
Use the netstat utility or the SHOW INTERFACE command to check
interface and protocol statistics, per-connection status, and memory buffer use.
Look for bad checksums, excessive retransmissions, dropped packets, out-of-order
packets, and lost-carrier errors.
TCPIP> netstat -i Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll TN0* 1280 Link Link#2 0 0 0 0 0 WF0 4470 Link 00:00:f8:cd:1e:e4 48855499 0 2035244 0 0 WF0 4470 16.20 ucxaxp 48855499 0 2035244 0 0 LO0 4096 Link Link#1 165084 0 165084 0 0 LO0 4096 127 LOCALHOST 165084 0 165084 0 0
If the output of the
netstat -icommand shows an excessive amounts of input errors (Ierrs), output errors (Oerrs), or collisions (Coll), this may indicate a network problem; for example, cables may not be connected properly or the Ethernet may be saturated.Memory problems
The
netstat -mcommand shows statistics for network-related data structures. Use this command to determine if the network is using an excessive amount of memory in proportion to the number of sockets in use.The
netstat -andisplays allocated sockets (each socket results in a network connection).Network connections
Use
netstat -anto check allocated sockets (each socket results in a network connection).
netstat -m command:TCPIP> netstat -m
1328 mbufs in use:
2 mbufs allocated to data
2 mbufs allocated to ancillary data
139 mbufs allocated to socket structures !
244 mbufs allocated to protocol control blocks "
442 mbufs allocated to routing table entries
2 mbufs allocated to socket names and addresses
26 mbufs allocated to interface addresses
1 mbufs allocated to ip multicast options
2 mbufs allocated to ip multicast addresses
5 mbufs allocated to interface multicast addresses
48 mbufs allocated to NFS request header
1 mbufs allocated to vnode struct
32 mbufs allocated to kern credential data structure
2 mbufs allocated to mbuf extra-data protocol message
58 mbufs allocated to assorted NFS structures
6 mbufs allocated to network interface structure
2 mbufs allocated to netisr thread queues
5 mbufs allocated to Inet PCB queues
1 mbufs allocated to rad specific structures
1 mbufs allocated to OpenVMS Cluster Alias table
37 mbufs allocated to OpenVMS Kernel VCI structure
12 mbufs allocated to OpenVMS TCPIP Timer structure
3 mbufs allocated to OpenVMS LAN VCI VCIB structure
3 mbufs allocated to OpenVMS LAN MCAST_REQ structure
12 mbufs allocated to OpenVMS SELECT structure
1 mbufs allocated to OpenVMS ACP Filter Buffer
1 mbufs allocated to OpenVMS ACP AQB
1 mbufs allocated to OpenVMS ACP INETCB
2 mbufs allocated to OpenVMS Driver requested REQCB
26 mbufs allocated to OpenVMS ACP allocated SERV Structure
37 mbufs allocated to OpenVMS VCI context block
1 mbufs allocated to OpenVMS ACP IPCACHE Structure
57 mbufs allocated to OpenVMS PROXY correlation records
66 mbufs allocated to OpenVMS PROXY host records
14 mbufs allocated to OpenVMS PROXY local user records
17 mbufs allocated to OpenVMS PROXY remote user records
17 mbufs allocated to OpenVMS Unix emulation stack (NFS, et al)
| This line indicates there are 24 sockets in use (1 mbuf allocated for each socket). |
| There are two protocol control blocks allocated for each TCP socket and one protocol control block for each UDP socket. The 35 mbuf listed is a mix of PCBs allocated for TCP and UDP sockets. Output from the TCPIP SHOW DEVICE_SOCKET command will tell you how many TCP and UDP sockets are allocated. |
By comparing the information output from the netstat -m and the TCPIP
command SHOW DEVICE_SOCKET, you can estimate whether the system is using an
excessive amount of memory for the number of allocated sockets.
If you sense that TCP/IP Services is using an excessive amount of memory for the
number of sockets, there may be a memory leak. Capture the output from the
netstat -m and the TCPIP SHOW DEVICE_SOCKET commands and save for
documenting the condition.
Table 1.2 shows variations of the netstat command that can reveal network problems.
netstat Commands|
Command |
Purpose |
|---|---|
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Checks for bad checksums, length problems, excessive redirects, and packets lost because of resource problems. |
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Checks for retransmissions, out of order packets, and bad checksums. |
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Looks for bad checksums and full sockets. |
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Obtains routing statistics. |
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Simultaneously displays statistics related to the IP, ICMP, TCP, and UDP protocol layers. |
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Checks for network device driver errors. |
For more information about netstat, see Appendix A
1.2.5. Monitoring Network Traffic
The TCPTRACE command, described in Section 1.2.5.1
The
tcpdumputility, described in Section 1.2.5.2
1.2.5.1. Using TCPTRACE
$ TCPTRACE HOST1 /FULL /PORT=REMOTE=21 $ TCPTRACE HOST2 /PORT=(LOCAL=23, REMOTE=1056) /FULL /PACKETS=30 /OUTPUT=TELNET_TRACE.TXT
TCPIP INTERnet trace RCV packet seq # = 1 at 23-OCT-1998 15:19:33.29
IP Version = 4, IHL = 5, TOS = 00, Total Length = 217 = ^x00D9
IP Identifier = ^x0065, Flags (0=0,DF=0,MF=0),
Fragment Offset = 0 = ^x0000, Calculated Offset = 0 = ^x0000
IP TTL = 32 = ^x20, Protocol = 17 = ^x11, Header Checksum = ^x8F6C
IP Source Address = 16.20.168.93
IP Destination Address = 16.20.255.255
UDP Source Port = 138, UDP Destination Port = 138
UDP Header and Datagram Length = 197 = ^x00C5, Checksum = ^x0E77
5DA81410 8F6C1120 00000065 D9000045 0000 E...awe.....l....]
| 0E77C500 8A008A00 | FFFF1410 0010 ..........w. For more information about using TCPTRACE, see Appendix A.
1.2.5.2. Using TCPDUMP
The OpenVMS tcpdump utility can trace natively on Ethernet or can
format traces taken on another host. It communicates with the TCP/IP kernel in
copy-all mode so it only can trace packets received or transmitted by the TCP/IP
kernel.
The trace can be taken interactively and ended with Ctrl/C, or continue until
a packet count has been reached (specified using -c
count). The tcpdump utility
displays a summary line indicating the number of packets traced and the number
of packets discarded by the kernel.
To use tcpdump, no special TCP/IP Services configuration is
required. The process using tcpdump must have OPER, PSWAPM, and
CMKRNL privileges.
How to build expressions (Section 1.2.5.2.1)
How to analyze output from
tcpdump(Section 1.2.5.3)Restrictions on using OpenVMS
tcpdump(Section 1.2.5.4)How to reduce discarded packets (Section 1.2.5.5)
1.2.5.2.1. Building Expressions
The expression is used to select the packets to dump. If no expression is given, all packets on the network are dumped. Otherwise, only packets for which expression is TRUE are dumped.
The expression consists of one or more primitives. Primitives usually consist of an identifier (name or number) preceded by one or more of the keywords described in Table 1.3
tcpdump Keywords| Keyword | Definition |
|---|---|
| type |
Defines the object to which the ID name or number
refers. The following types are allowed:
For example: host foo net 128.3 port 20 If no type keyword is specified, host is the default. |
| dir |
Specifies a particular transfer direction to or from
id. The following
directions are allowed:
For example: src foo dst net 128.3 src or dst port 20 src and dst port 123 If no dir keyword is specified, src or dst is the default. |
| proto |
Restricts the match to a particular protocol. The
following protocols are allowed:
For example: ether src foo arp net 128.3 tcp port 21 If no proto keyword
is specified, all protocols consistent with the
type are assumed.
For example, (ip or arp or rarp) src foo (Note that the latter is not valid syntax.) net bar means: (ip or arp) net bar port 53 means: (tcp or udp) port 53 |
1.2.5.2.2. Keywords for Filtering Traces from non-OpenVMS Systems
etherfddiipipv6icmpv6arprarpdecnetlatmoprcmopdltcpudp
1.2.5.2.3. Primitive Keywords
gatewaybroadcastlessgreaterArithmetic expressions
host foo and not port ftp and not port ftp-data
tcp dst port ftp or ftp-data or domain tcp dst port ftp or tcp dst port ftp-data or tcp dst port domain
1.2.5.2.4. Primitive Expressions
dst host hostTrue if the IP destination field of the packet is host, which may be either an address or a name.
src host hostTrue if the IP source field of the packet is host.
host hostTrue if either the IP source or destination of the packet is host. The following keywords can precede any of these host expressions:iparprarp
The following examples are equivalent:ip host host ether proto ip and host host
ether dst ehostTrue if the Ethernet destination address is ehost.
ether src ehostTrue if the Ethernet source address is ehost.
ether host ehostTrue if either the Ethernet source or destination address is ehost.
gateway hostTrue if the packet used host as a gateway. That is, the Ethernet source or destination address was host but neither the IP source nor the IP destination was host.
This expression is equivalent to the following:ether host ehost and not host host
dst net net(IPv4 networks only) True if the IP destination address of the packet has a network number of net, which may be either an address or a name.
src net net(IPv4 networks only) True if the IP source address of the packet has a network number of net.
net net(IPv4 networks only) True if either the IP source or destination address of the packet has a network number of net.
dst port portTrue if the packet is IP/TCP or IP/UDP and has a destination port value of port.
src port portTrue if the packet has a source port value of port.
port portTrue if either the source or destination port of the packet is port. The following keywords can precede any of these port expressions:tcpudp
For example, the following example matches only TCP packets:tcp src port portless lengthTrue if the packet has a length less than or equal to length. The following example is equivalent:len <= lengthgreater lengthTrue if the packet has a length greater than or equal to length. The following example is equivalent:len >= lengthip proto protocolTrue if the packet is an IP packet of protocol type protocol. The protocol can be a number, or one of the following names:ipv6icmpicmpv6udpndtcp
ether broadcast
True if the packet is an Ethernet broadcast packet. The ether keyword is optional.
ip broadcast
(IPv4 networks only) True if the packet is an IP broadcast packet. It checks for both the all-zeroes and all-ones broadcast conventions, and looks up the local subnet mask.
ether multicast
True if the packet is an Ethernet multicast packet. The ether keyword is optional. This is shorthand for:ether[0] & 1 != 0
ip multicast(IPv4 networks only) True if the packet is an IPv4 multicast packet.
ether proto protocolTrue if the packet is of protocol type ether. The protocol argument can be a number or a name, such as
ip,ipv6, andarp.Only Ethernet is supported with protocols ip, ipv6 and arp for native tracing. If reading a trace created on another platform, tcpdump will be able to filter and format it correctly.
expr relop exprTrue if the relation holds, where relop is one of the following:><>=<==,!=
expr is an arithmetic expression composed of integer constants (expressed in standard C syntax), the normal binary operators [+, -, *, /, &, | ], a length operator, and special packet data accessors.
1.2.5.2.5. Accessing Data Inside Packets
proto [expr : size]
- The proto variable is one of the following:
etherfddiiparprarptcpudpicmp
The proto variable indicates the protocol layer for the index operation.
The byte offset, relative to the indicated protocol layer, is specified by expr.
- The size variable is optional and indicates the number of bytes in the field of interest; it can be:
onetwoorfour
The default size is
one.
For example:
ether[0]&1!=0detects all multicast traffic.ip[0] & 0xf != 5detects all IP packets with options.ip[2:2] & 0x1fff = 0detects only unfragmented datagrams and fragment zero of fragmented datagrams. This check is implicitly applied to the TCP and UDP index operations. For instance,tcp[0]always means the first byte of the TCP header, and never means the first byte of an intervening fragment.
1.2.5.2.6. Combining Keywords
Keywords can be combined using:
A parenthesized group of primitives and operators
Negation (
!ornot)Concatenation (
and)Alternation (
or)
Negation has highest precedence. Alternation and concatenation have equal precedence and associate left to right. Note that explicit and tokens (not juxtaposition) are required for concatenation.
not host vs and ace not host vs and host ace
not ( host vs or ace )
Expression arguments can be passed to tcpdump as either a
single argument or as multiple arguments, whichever is more convenient.
Multiple arguments are concatenated with spaces before being parsed.
1.2.5.3. Analyzing Output
The output of the tcpdump utility is protocol dependent. The
following sections describe the formats and provide examples.
1.2.5.3.1. Link Level Headers
The -e option is used to display the link level header. On
Ethernet networks, the source and destination addresses, protocol, and
packet length are displayed.
Only Ethernet frame types are supported with tcpdump.
1.2.5.3.2. ARP Packets
rtsg to host
csam:arp who-has csam tell rtsg arp reply csam is-at CSAM
The first line indicates that host rtsg sent an ARP packet asking for the Ethernet address of Internet host csam. Host csam replies with its Ethernet address (in this example, Ethernet addresses are uppercase and Internet addresses in lowercase).
arp who-has 128.3.254.6 tell 128.3.254.68 arp reply 128.3.254.6 is-at 02:07:01:00:01:c4
tcpdump -e command, the first packet is
explicitly a broadcast packet and the second is a point-to-point
packet:RTSG Broadcast 0806 64: arp who-has csam tell rtsg CSAM RTSG 0806 64: arp reply csam is-at CSAM
For the first packet, the Ethernet source address is RTSG, the destination is the broadcast address, the type field contain hex 0806 (type ETHER_ARP) and the total length is 64 bytes.
1.2.5.3.3. TCP Packets
The following description assumes familiarity with the TCP protocol described in RFC 793.
src > dst: flags data-seqno ack window options
The fields represent the following:
src
The source IP addresses and ports.
dst
The destination IP addresses and ports.
flags
The sum combination of S (SYN), F (FIN), P (PUSH), or R (RST) or a single period (.) for no flags.
data-seqno
The portion of sequence space covered by the data in this packet (see the example below).
ack
The sequence number of the next data expected from the other direction on this connection.
window
The number of bytes of receive buffer space available from the other direction on this connection.
urgentIndicates there is urgent data in the packet.
options
The TCP options enclosed in angle brackets. For example:<mss 1024>
The src, dst, and flags fields are
always present. The other fields depend on the contents of the packet's TCP
protocol header and are output only if appropriate.
Examples
rtsg.1023 > csam.login: S 768512:768512(0) win 4096 <mss 1024> csam.login > rtsg.1023: S 947648:947648(0) ack 768513 win 4096 <mss 1024> rtsg.1023 > csam.login: . ack 1 win 4096 rtsg.1023 > csam.login: P 1:2(1) ack 1 win 4096 csam.login > rtsg.1023: . ack 2 win 4096 rtsg.1023 > csam.login: P 2:21(19) ack 1 win 4096 csam.login > rtsg.1023: P 1:2(1) ack 21 win 4077 csam.login > rtsg.1023: P 2:3(1) ack 21 win 4077 urg 1 csam.login > rtsg.1023: P 3:4(1) ack 21 win 4077 urg 1
The example shows the following sequence of communication:
The first line indicates that TCP port 1023 on system rtsg sent a packet to port login on host csam. The S indicates that the SYN flag was set. The packet sequence number was 768512 and it contained no data. (The notation is first:last(nbytes), which means sequence numbers first up to but not including last, which is nbytes bytes of user data.) There was no piggy-backed ack, the available receive window was 4096 bytes and there was a
max-segment-sizeoption requesting an mss of 1024 bytes.Host csam replies with a similar packet except that it includes a piggy-backed ack for the SYN sent by rtsg.
Host rtsg then sends an ack reply to the SYN sent by csam. The period (.) means no flags were set. The packet contained no data, so there is no data sequence number. Note that the ack sequence number is a small integer (1). The first time tcpdump sees a TCP conversation, it displays the sequence number from the packet.
On subsequent packets of the conversation, the difference between the current packet's sequence number and this initial sequence number is displayed. Thus, sequence numbers after the first can be interpreted as relative byte positions in the conversation's data stream (with the first data byte each direction being 1). The -S option overrides this feature, causing the original sequence numbers to be output.
The sixth line indicates that host rtsg sends host csam 19 bytes of data (bytes 2 through 20 in the rtsg-to-csam side of the conversation). The PUSH flag is set in the packet.
The seventh line indicates that host csam has received data sent by host rtsg up to but not including byte 21. Most of this data is apparently sitting in the socket buffer because the receive window on host csam is 19 bytes smaller. Host csam also sends one byte of data to host rtsg in this packet.
The eighth and ninth lines show that host csam sends two bytes of urgent, pushed data to rtsg.
1.2.5.3.4. UDP Packets
actinide.who > broadcast.who: udp 84
This line of output indicates that port who on host actinide sent a UDP datagram to port who on host broadcast, the Internet broadcast address. The packet contained 84 bytes of user data.
Some UDP services are recognized (from the source or destination port number) and the higher level protocol information displayed, specifically Domain Name service requests (RFC 1034 and RFC 1035) and Sun RPC calls (RFC 1050) to NFS.
1.2.5.3.5. UDP Name Server Requests
The following description assumes familiarity with the Domain Service protocol described in RFC 1035.
src > dst: id op? flags qtype qclass name (len)h2opolo.1538 > helios.domain: 3+ A? ucbvax.berkeley.edu. (37)
Host h2opolo queried the domain server on host helios for an address record (qtype=A) associated with the name ucbvax.berkeley.edu. The query ID was 3. The plus sign (+) indicates the recursion desired flag was set. The query length was 37 bytes, not including the UDP and IP protocol headers. The query operation was the normal one, Query, so the op field was omitted. If the op field had been anything else, it would have been displayed between the 3 and the plus sign (+). Similarly, the qclass was the normal one, C_IN, and omitted. Any other qclass would have been displayed immediately after the A.
The following anomalies are checked and may result in extra fields enclosed in square brackets:
If a query contains an answer, name server, or authority section, ancount, nscount, or arcount are displayed as [na], [nn] or [nau], where n is the appropriate count.
If any of the response bits are set (AA, RA or rcode) or any of the "must be zero" bits are set in bytes 2 and 3, [b2&3=x]) is displayed, where x is the hexadecimal value of header bytes 2 and 3.
1.2.5.3.6. UDP Name Server Responses
src > dst: id op rcode flags a|n|au type class data (len)helios.domain > h2opolo.1538: 3 3/3/7 A 128.32.137.3 (273) helios.domain > h2opolo.1537: 2 NXDomain* 0/1/0 (97)
In the first example, host helios responds to query ID 3 from host h2opolo with 3 answer records, 3 name server records, and 7 authority records. The first answer record is type A (address) and its data is Internet address 128.32.137.3. The total size of the response is 273 bytes, excluding UDP and IP headers. The op (Query) and response code (NoError) are omitted, as is the class (C_IN) of the A record.
In the second example, host helios responds to query 2 with a response code of nonexistent domain (NXDomain) with no answers, one name server and no authority records. The asterisk (*) indicates that the authoritative answer bit is set. Since there are no answers, no type, class, or data are displayed.
Other flag characters that might appear are the minus sign (-) (recursion available, RA, not set) and vertical bar ( | ) (truncated message, TC, set). If the "question" section does not contain exactly one entry, [nq] is displayed.
Note that name server requests and responses tend to be large, and the default value of snaplen, 96 bytes, may not capture enough of the packet to print. Use the -s option to increase the snaplen if you need to seriously investigate name server traffic.
1.2.5.3.7. Sun RPC Requests and Replies
Sun RPC (RFC 1057) is decoded as described in Table 1.4, as are several of the protocols that use Sun RPC.
| Name | Users | Description |
|---|---|---|
|
PORTMAP |
libc.a, portmap |
Maps RPC program numbers to TCP/UDP ports. |
|
MOUNT |
mount, mountd |
Maps file names to NFS file handles. |
|
NLM |
rpc.lockd |
NFS remote file locking. |
|
STAT |
rpc.statd, rpc.lockd |
Remote status monitor. |
|
YP |
libc.a, ypserv |
Network Information Services. |
|
YPBIND |
ypbind, ypset |
NIS domain manipulation. |
|
NFS |
UNIX |
Network File System. |
Requests sent using TCP must start at the beginning of a packet to be decoded. Normally they are; however, applications that have multiple requests outstanding (for example, NFS) may not always do this.
Replies can only be decoded if the request was found and only if they start a packet.
src.xid > dst.prot-vn: len call op args
src.xid > dst.prot-vn: len reply op resultsclnt.312dbc68 > svc.pmap-v2: 56 call getport prog "nfs" V3 prot UDP po0
svc.312dbc68 > clnt.pmap-v2: 28 reply getport 2049
clnt.312deff8 > svc.pmap-v2: 56 call getport prog "mount" V3 prot UDP 0
svc.312deff8 > clnt.pmap-v2: 28 reply getport 1034
clnt.312deff8 > svc.mount-v3: 124 call mount "/build"
svc.312deff8 > clnt.mount-v3: 68 reply mount OSF/1 fh 8,3079/1.2
clnt.907312 > svc.nfs-v3: 148 call getattr OSF/1 fh 8,3079/1.2
svc.907312 > clnt.nfs-v3: 112 reply getattr {dir size 1024 mtime ... }-m and -v options are in effect, both RPC and
TCP decoding are done. For example, the UNIX command showmount -e
srv generates information such as the
following:clnt.3123f473 > svc.pmap-v2: 56 call getport prog "mount" V1 prot TCP 0
(ttl 29, id 19672)
svc.3123f473 > clnt.pmap-v2: 28 reply getport 892
(ttl 30, id 31644)
clnt.1032 > svc.892: S 25280000:25280000(0) win 32768 <mss 1460,nop,wsca>
(DF) (ttl 59, id 19674)
svc.892 > clnt.1032: S 483136000:483136000(0) ack 25280001 win 33580
<mss 1460,nop,wscale 0> (ttl 60, id 31645)
clnt.1032 > svc.892: . ack 1 win 33580 (DF) (ttl 59, id 19675)
clnt.2f221c23 > svc.mount-v1: 40 call return export list
TCP: clnt.1032 > svc.892: P 1:45(44) ack 1 win 33580 (DF) (ttl 59, id 19)
svc.2f221c23 > clnt.mount-v1: 184 reply export
"/usr": "client" "clnt"
"/build":
...
TCP: svc.892 > clnt.1032: P 1:189(188) ack 45 win 33580 (ttl 60, id 3164)
clnt.1032 > svc.892: F 45:45(0) ack 189 win 33580 (DF) (ttl 59, id 19679)
svc.892 > clnt.1032: . ack 46 win 33580 (ttl 60, id 31649)
svc.892 > clnt.1032: F 189:189(0) ack 46 win 33580 (ttl 60, id 31650)
clnt.1032 > svc.892: . ack 190 win 33580 (DF) (ttl 59, id 19681)
sushi.6709 > wrl.nfs-v2: 112 call readlink fh 21,24/10.731657119 wrl.6709 > sushi.nfs-v2: 40 reply readlink "../var" sushi.201b > wrl.nfs-v2: 144 call lookup fh 9,74/4096.6878 "xcolors" wrl.201b > sushi.nfs-v2: 128 reply lookup fh 9,74/4134.3150
The example shows the following sequence of communication:
In the first line, host
sushisends a transaction with ID 6709 to hostwrl. (The number following thesrchost is a transaction ID, not the source port.) The request was 112 bytes, excluding the UDP and IP headers. The operation was a readlink (read symbolic link) on file handle (fh) 21,24/10.731657119. (In some cases, the file handle can be interpreted as a major and minor device number pair, followed by the inode number and generation number.) Hostwrlreplies with the contents of the link.In the third line, host
sushiasks hostwrlto look up the namexcolorsin directory file 9,74/4096.6878.The data displayed depends on the operation type. The format is intended to be self explanatory if read in conjunction with a protocol specification rpcgen
.xfile.
If the -v (verbose) option is given, additional information
is displayed.
If the -v option is given more than once, more details may be
displayed.
tcpdump. For
example:node1.abc.com.da31fba5 > node2.abc.com.proplist-v3: \
276 call proproc3_get OSF/1 fh 8,18434/1.4 mask:-1 11 entries
node2.abc.com.da31fba5 > node1.abc.com.proplist-v3: \
296 reply proproc3_get status OK 368 bytes 11 entries
For property list calls, you can request the mask value and the number of property list entries. Property list replies return the status, the number of bytes in the property list and the number of entries in property list.
Note that NFS requests are very large and much of the detail is not
displayed unless the value of snaplen is
increased. Use -s 192 to watch RPC traffic.
RPC reply packets do not explicitly identify the RPC operation. Instead, tcpdump keeps track of recent requests, and matches them to the replies using the transaction ID. If a reply does not closely follow the corresponding request, it might not be parsable.
1.2.5.3.8. IP Fragmentation
(frag id:size@offset+) (frag id:size@offset)
The first line indicates there are more fragments. The second indicates this is the last fragment.
The following list explains the fields:
id is the fragment ID.
size is the fragment size (in bytes), excluding the IP header.
offset is the fragment's offset (in bytes) in the original datagram.
arizona.ftp-data > rtsg.1170: . 1024:1332(308) ack 1 win 4096 (frag 595a:328@0+) arizona > rtsg: (frag 595a:204@328) rtsg.1170 > arizona.ftp-data: . ack 1536 win 2560
Note the following:
Addresses in the second line do not include port numbers. This is because the TCP protocol information is in the first fragment and
tcpdumpdoes not know what the port or sequence numbers are when it displays the later fragments.TCP sequence information in the first line is displayed as if there were 308 bytes of user data; however, there are 512 bytes (308 in the first fragment and 204 in the second). If you are looking for holes in the sequence space or trying to match up acknowledgements with packets, this can be misleading.
A packet with the IP "do not fragment" flag is marked with a trailing (DF).
1.2.5.3.9. Timestamps
hh:mm:ss.fracIt is as accurate as the kernel's clock. The timestamp reflects the time the kernel first saw the packet. No attempt is made to account for the time difference between when the Ethernet interface removed the packet from the wire and when the kernel serviced the new packet interrupt.
1.2.5.4. Restrictions
The following restrictions apply to using tcpdump on
OpenVMS:
Copy-all mode is on by default on OpenVMS.
Promiscuous mode is not available, so tracing must be issued on either the source or destination host.
Only Ethernet native tracing on is supported on OpenVMS.
Only one user may trace at a time on OpenVMS using either
tcpdumportcptrace.Name server inverse queries are not dumped correctly: The (empty) question section is displayed rather than real query in the answer section.
A packet trace that crosses a daylight saving time change produces skewed time stamps (the time change is ignored).
1.2.5.5. Reducing Discarded Packets
When packets are copied by the TCP/IP kernel, it places them into a ring
buffer that is emptied by tcpdump. If packets are received fast
enough, the ring will fill up and the TCP/IP kernel discards (drops) packets
until tcpdump has caught up. Because tcpdump has not seen these
dropped packets, it cannot tell whether they were relevant to the requested
trace.
If the option -B is used, tcpdump indicates when the
drops occur by issuing a BUFFERSFULL error. This can be useful if the drops
occur outside the sequence being analyzed.
There are several methods for reducing the number of packet drops:
Specify a more detailed filter in the
tcpdumpcommand. Trace to a file instead of SYS$OUTPUT using-wfilename. For best results, use a disk with little activity or a RAM disk.Increase the number of buffers in the ring using
-bbuffers. The default for Alpha systems is 400. For VAX systems, the default is 50. The processes working set quota (WSQUOTA) may need to be increased for larger numbers than the default.Increase the default process priority of the process that issued the tcpdump
command.
1.2.6. Monitoring Socket Activity
TCP/IP Services provides a call tracing facility that can be used to help characterize and debug the use of the sockets API for many applications.
To enable tracing, define the TCPIP$SOCKET_TRACE logical name. The logical name accepts the following arguments:
1 or 0
Specify 1 to enable socket tracing, or 0 to disable socket tracing. When the logical name is set to 1, the output from the trace is displayed interactively. For example:$ DEFINE TCPIP$SOCKET_TRACE 1
Log file name
Specify the name of the log file for storing the tracing information. For example:$ DEFINE TCPIP$SOCKET_TRACE SYS$LOGIN:TCPIP$SOCKET_TRACE.LOG
Location for process-specific log files
Specify a directory for storing the log files. Each log file name reflects the name of the process that is being traced. For example:$ DEFINE /SYSTEM TCPIP$SOCKET_TRACE SYS$SYSDEVICE:[LOGFILES]
23:35:47.48 +socket family: 2, type: 1, proto: 0 23:35:47.48 -socket chan: 0xf0, st: 0x1, iosb: 0x1 0 23:35:47.48 *setsockopt sock: 0xf0, lev: 0xffff, opt: 0x4, val: 1, len: 4 23:35:47.49 *bind44 socket: 0xf0, st: 0x1, iosb: 0x1 0 23:35:47.50 *listen sock: 0xf0, backlog: 5 23:35:47.51 +accept44 chan: 0xf0 23:35:54.04 -accept44 rtchan: 0x100, st: 0x1, iosb: 0x1 0 23:35:54.04 *getpeername44 sock: 0x100 23:35:54.04 +send_64 sock: 0x100, addr: 0x7AEF7A00, len: 28, flags: 0x0 23:35:54.04 -send_64 st: 0x1, iosb: 0x1 28 23:35:54.04 *shutdown sock: 0x100, how: 2 23:35:54.05 *close sock: 0x100, st: 0x1 23:35:54.05 *close sock: 0xf0, st: 0x1
In this example, you can see the application opening a socket, setting socket options, binding, listening, accepting, sending data, and so forth.
Lines beginning with a plus sign (+) indicate that the relevent routine is being entered. There is usually a line beginning with a minus sign (-) soon after, when the routine returns. For routines that normally return right away, only one line is displayed, beginning with an asterisk (*).
Note
This facility does not trace QIOs and other system services.
1.2.7. Checking Name Server Operation
TCPIP> SHOW NAME_SERVICE BIND Resolver Parameters Local domain: lkg.dec.com System State: Started, Enabled Transport: UDP Domain: lkg.dec.com Retry: 4 Timeout: 4 Servers: rufus.lkg.dec.com, peach.lkg.dec.com Path: lkg.dec.com Process State: Enabled Transport: Domain: Retry: Timeout: Servers: Path:
Make sure the
remote servers are reachable (using ping) and that they are valid name
servers.
If your name server resides on the local system, use the SHOW NAME_SERVICE command
to make sure your resolver points to localhost.
TCPIP> SHOW SERVICE Service Port Proto Process Address State BIND 53 TCP,UDP TCPIP$BIND 0.0.0.0 Enabled DHCP 67 UDP TCPIP$DHCP 0.0.0.0 Enabled DIOSERVER 1451 TCP CLM 0.0.0.0 Disabled ECHO 7 TCP MULTI 0.0.0.0 Disabled ESNMP 705 UDP ESNMP 0.0.0.0 Disabled FINGER 79 TCP TCPIP$FINGER 0.0.0.0 Enabled FTP 21 TCP TCPIP$FTP 0.0.0.0 Enabled HELLO 12345 TCP HELLO_WORLD 0.0.0.0 Disabled JOHN 520 UDP UCX$ROUTER 0.0.0.0 Disabled LBROKER 6570 UDP TCPIP$LBROKER 0.0.0.0 Disabled LPD 515 TCP TCPIP$LPD 0.0.0.0 Enabled MATT 5432 TCP TCPIP$RLOGIN 0.0.0.0 Disabled METRIC 570 UDP TCPIP$METRIC 0.0.0.0 Enabled MOUNT 10 TCP,UDP TCPIP$MOUNTD 0.0.0.0 Enabled NFS 2049 UDP TCPIP$NFS 0.0.0.0 Enabled NOTES 3333 TCP NOTESRVR 0.0.0.0 Enabled NTP 123 UDP TCPIP$NTP 0.0.0.0 Enabled PCNFS 5151 TCP,UDP TCPIP$PCNFSD 0.0.0.0 Enabled POP 110 TCP TCPIP$POP 0.0.0.0 Enabled PORTMAPPER 111 TCP,UDP TCPIP$PORTM 0.0.0.0 Enabled REXEC 512 TCP TCPIP$REXEC 0.0.0.0 Enabled RLOGIN 513 TCP not defined 0.0.0.0 Enabled RSH 514 TCP TCPIP$RSH 0.0.0.0 Enabled SMTP 25 TCP TCPIP$SMTP 0.0.0.0 Enabled SNMP 161 UDP TCPIP$SNMP 0.0.0.0 Enabled TELNET 23 TCP not defined 0.0.0.0 Enabled TFTP 69 UDP TCPIP$TFTP 0.0.0.0 Enabled XDM 177 UDP TCPIP$XDM 0.0.0.0 Enabled
If the BIND process is enabled, it will appear in the display.
$ SHOW SYSTEM /NETWORK OpenVMS V7.1-1H2 on node RUFUS 27-JUN-2000 16:45:46.84 Uptime 16 01:55:35 Pid Process Name State Pri I/O CPU Page flts Pages 2FC0021F TCPIP$NTP LEF 10 2042786 0 00:02:03.43 657 190 N 2FC00221 TCPIP$LBROKER LEF 9 3779921 0 00:06:27.51 652 271 N 2FC05046 TCPIP$POP_1 HIB 10 243688 0 00:00:48.42 955 598 N 2FC00289 TCPIP$PORTM LEF 10 13289 0 00:00:03.23 614 189 N 2FC0628F TCPIP$RE_BG1879 LEF 6 1647 0 00:00:00.96 1709 612 N 2FC0089A NFS$SERVER LEF 10 89284 0 00:00:19.28 978 580 N 2FC06C9E NOTES$00CD_2* HIB 6 208844 0 00:01:22.65 1932 152 N 2FC03EC7 TCPIP$BIND_1 LEF 10 515297 0 00:01:26.06 972 322 N 2FC01CF6 TCPIP$PCNFSD LEF 10 326 0 00:00:00.27 660 228 N
If the TCPIP$BIND_1 process is not running, look for errors in the SYS$SPECIFIC:[TCPIP$BIND]TCPIP$BIND_RUN.LOG file.
To reduce the possibility of a name server being unavailable, you might configure more than one name server on your network. This way, if the primary name server is unreachable or unresponsive, the resolver can query the other name server.
1.2.8. Checking the Route to a Remote Host
Enter a
netstat -rnor SHOW ROUTE command.Display the routing table, then compare the output to the routing table of a properly running system. Make sure there is a default route defined and that the IP address listed in the gateway column for the default route and the local host are in the same subnet. The default route specifies the gateway to use when a route is not explicitly defined for the destination IP address.
For example, enter the following command:TCPIP> netstat -rn Routing tables Destination Gateway Flags Refs Use Interface Route Tree for Protocol Family 2 default 16.20.0.173 UG 17 1526068 WE0 10.10/16 16.20.208.154 UGS 0 204911 WE0 10.10.39/25 10.10.39.2 U 2 17942 BE0 16.20/16 16.20.208.100 U 45 6219676 WE0 16.20/16 16.20.208.208 U 0 0 WE0 127.0.0.1 127.0.0.1 UH 1 69844 LO0 Route Tree for Protocol Family 26 ::1 Link#1 UH 0 0 LO0 ff01::/16 Link#1 U 0 0 LO0
- To display a default route using the VSI TCP/IP Services management commands, enter one of the following commands:
$ TCPIP SHOW ROUTE /PERMANENT /DEFAULT $ TCPIP SHOW ROUTE /DEFAULT
The following example shows typical output from these two commands:$ TCPIP SHOW ROUTE /PERMANENT /DEFAULT PERMANENT Type Destination Gateway PN 0.0.0.0 rufus.lkg.dec.com $ TCPIP SHOW ROUTE /DEFAULT DYNAMIC Type Destination Gateway DN 0.0.0.0 10.10.2.66 $To set a default route, enter a command similar to the following:$ TCPIP SET ROUTE /DEFAULT /GATE=n.n.n.nYou can also set a default route by running the TCPIP$CONFIG procedure and selecting option 1 for Core, and then option 3 for Routing. TCPIP$CONFIG prompts with:* Do you want to configure dynamic ROUTED or GATED routing [NO]:
Take the default value by pressing the Enter key. TCPIP$CONFIG then displays the current configuration and asks whether you want to reconfigure a default route:The current configuration for the default route is: PERMANENT Type Destination Gateway PN 0.0.0.0 rufus.lkg.dec.com * Do you want to reconfigure a default route [YES]: Enter the Default Gateway host name []: Next, use
pingto see whether you can reach the routing gateway.
1.2.9. Checking the Routes Known to a Gateway
The traceroute command helps you locate problems between the local
host and the remote destination by tracing the route of UDP packets from the local
host to a remote host. Tracing attempts to determine the name and IP address of each
gateway along the route to the remote host.
The traceroute command works by sending UDP packets with small
time-to-live (TTL) values and an invalid port number to the remote system. The TTL
values increase in increments of one for each group of three UDP packets sent. When
a gateway receives a packet, it decrements the TTL. If the TTL is zero, the packet
is not forwarded, and an ICMP “time exceeded” message is
returned.
Intermediate gateways are detected when they return an ICMP “time
exceeded” message. When traceroute receives an
“invalid port” message, it knows that it reached the remote
destination.(traceroute operates by intentionally using an invalid
port.) When traceroute receives this message, it knows it has reached
the destination host and terminates the trace. In this way, traceroute
develops a list of gateways starting at one hop away, and increasing one hop at a
time until the remote host is reached.
For more information about using traceroute, see Appendix A.
1.2.10. Determine Whether Network Services Are Available
The auxiliary server functions
like the UNIX internet daemon (inetd) by managing access to the network
services. The auxiliary server assigns standard port numbers to services such as the
BOOTP, SMTP, or FTP servers, and starts the appropriate image after receiving an
incoming request.
Has an entry in the service database
Has the correct attributes defined
Account has the correct privileges
Is enabled
Is started
1.2.10.1. Displaying the Service Database
TCPIP> SHOW SERVICE
Service Port Proto Process Address State FINGER 79 TCP TCPIP$FINGER 0.0.0.0 Disabled FTP 21 TCP TCPIP$FTP 0.0.0.0 Enabled LPD 515 TCP TCPIP$LPD 0.0.0.0 Enabled MOUNT 10 UDP TCPIP$NFS_M 0.0.0.0 Enabled NFS 2049 UDP TCPIP$NFS 0.0.0.0 Enabled NTP 123 UDP TCPIP$NTP 0.0.0.0 Enabled PCNFS 5151 TCP,UDP TCPIP$PCNFSD 0.0.0.0 Enabled POP 110 TCP TCPIP$POP 0.0.0.0 Enabled PORTMAPPER 111 TCP,UDP TCPIP$PORTM 0.0.0.0 Enabled REXEC 512 TCP TCPIP$REXEC 0.0.0.0 Enabled RLOGIN 513 TCP not defined 0.0.0.0 Enabled RSH 514 TCP TCPIP$RSH 0.0.0.0 Enabled SMTP 25 TCP TCPIP$SMTP 0.0.0.0 Enabled SNMP 161 UDP TCPIP$SNMP 0.0.0.0 Enabled TELNET 23 TCP not defined 0.0.0.0 Enabled TFTP 69 UDP TCPIP$TFTP 0.0.0.0 Enabled
| This column lists those services with entries in the TCPIP services database. If not listed in this column, the service was never enabled during the configuration procedure (using TCPIP$CONFIG.COM). To enable additional services, run the TCPIP$CONFIG procedure. |
| This column lists the port on which the service listens for connection requests. The port number is either the well-known port number for the service or an ephemeral port number assigned when the socket is assigned a protocol address. |
| This column lists the TCP/IP protocol that the service uses to communicate with the client process. |
| This column lists the process name for the service. If you use the DCL command SHOW SYSTEM /NETWORK, this is the process name you should see if the process is running. |
| This column lists the IP address of the interface on which the service accepts connection requests. IP address 0.0.0.0 indicates that the service will accept connection requests received on any of the local interfaces. |
| This column lists whether the service is enabled or disabled. The
term enabled indicates that the next time VSI TCP/IP Services starts,
VSI TCP/IP Services starts all services that are marked in the service
database as enabled. In this example, of the services listed, all
services except finger will start the next time
VSI TCP/IP Services restarts. NoteIn this example, the |
1.2.10.2. Displaying Service Attributes
OpenVMS user account (also in user authorization file [UAF])
Unique port number
Protocol
Name and location of the startup command procedure and log file
Service parameters (for example, timeouts, privileges)
Flags
If these items are not defined correctly, or if the service account privileges and file protections are not assigned correctly, the service will fail to respond to an incoming request. This failure may be logged in the service-specific log file.
$ TCPIP TCPIP> SHOW SERVICE /FULL TELNET Service: TELNET
| This section displays information about the service: service name, process name, user name, port and interface on which the service is listening, whether the service is enabled or disabled, and the number of copies of the service that can run at one time. |
| This section displays the socket options that the service uses. The service's socket options can be changed dynamically, though it is unlikely that someone would change them. If you suspect that improper socket options are in effect, you can reestablish the default values by disabling the service, running TCPIP$CONFIG, and then enabling the service. |
| This section displays the name of the log file that receives event messages and the events that the service will log. Checking the log file may indicate the cause of a problem. |
| This security section displays a list of hosts and networks that are specifically given or denied access to the service. If one system is unable to access a service, check this section to see whether the system or its associated network is being denied the service. |
1.2.10.3. Verifying Process Privileges
$ INSTALL LIST/FULL TCPIP$SMTP_RECEIVER
DISK$VMS721:<SYS0.SYSCOMMON.SYSEXE>.EXE
TCPIP$SMTP_RECEIVER;1
Open Hdr Shared Prv
Entry access count = 20
Current / Maximum shared = 1 / 1
Global section count = 1
Privileges = SYSPRV
Authorized = SYSPRV
$ INSTALL LIST/FULL TCPIP$FTP_CHILD
DISK$VMS721:<SYS0.SYSCOMMON.SYSEXE>.EXE
TCPIP$FTP_CHILD;1
Open Hdr Shared Prv
Entry access count = 42
Current / Maximum shared = 1 / 3
Global section count = 1
Privileges = PSWAPM OPER
Authorized = PSWAPM OPER 1.2.10.4. Verifying Account Privileges
A72KT: SET DEFAULT SYS$SYSTEM A72KT: RUN AUTHORIZE UAF> SHOW TCPIP$SNMP Username: TCPIP$SNMP Owner: TCPIP$SNMP Account: TCPIP UIC: [3655,13] ([TCPIP$AUX,TCPIP$S NMP]) CLI: DCL Tables: DCLTABLES Default: SYS$SYSDEVICE:[TCPIP$SNMP] LGICMD: LOGIN Flags: Restricted Primary days: Mon Tue Wed Thu Fri Secondary days: Sat Sun Primary 000000000011111111112222 Secondary 000000000011111111112222 Day Hours 012345678901234567890123 Day Hours 012345678901234567890123 Network: ##### Full access ###### ##### Full access ###### Batch: ----- No access ------ ----- No access ------ Local: ----- No access ------ ----- No access ------ Dialup: ----- No access ------ ----- No access ------ Remote: ----- No access ------ ----- No access ------ Expiration: (none) Pwdminimum: 6 Login Fails: 0 Pwdlifetime: 90 00:00 Pwdchange: (pre-expired) Last Login: (none) (interactive), 7-AUG-2000 12:45 (non-interactive) Maxjobs: 0 Fillm: 50 Bytlm: 52200 Maxacctjobs: 0 Shrfillm: 0 Pbytlm: 0 Maxdetach: 0 BIOlm: 18 JTquota: 4096 Prclm: 8 DIOlm: 18 WSdef: 350 Prio: 8 ASTlm: 100 WSquo: 512 Queprio: 4 TQElm: 15 WSextent: 512 CPU: (none) Enqlm: 100 Pgflquo: 10240 Authorized Privileges: NETMBX TMPMBX Default Privileges: NETMBX TMPMBX
1.2.10.5. Looking for OPCOM Messages
- Enter the following commands:
$ SET PROCESS /PRIVILEGE=OPER
$ SET AUDIT /ALARM /ENABLE=FAILURE
$ REPLY/ENABLE=NETWORK Enables your process with operator privileges.
Enables security auditing to log unsuccessful object attempts.
Establishes your terminal as an operator's terminal.
After you enter these commands, have a remote user try to connect to the service on the local system.
Review any OPCOM messages for indications of the problem.
1.3. Using Online Help
CP/IP Services provides online help for commands, utilities, and error messages.
For information about using TCP/IP management commands, enter the HELP command from the TCP/IP management control program.
$ TCPIP TCPIP> HELP SYSCONFIG
$ HELP FTP
$ FTP FTP> HELP
Commands for obtaining online information from the application user interface are application specific. Refer to the description of the application in the VSI TCP/IP Services for OpenVMS User's Guide for specific instructions.
$ HELP/MESSAGE FTP_CONHST
FTP_CONHST, error connecting to remote host 'host'
Facility: TCPIP, FTP Server
Explanation: An error occurred in the FTP client. A network error occurred
or the network is not active.
User Action: Make sure network communication is active on the system.1.4. Using OpenVMS ANALYZE Extensions
$ ANALYZE/SYSTEM SDA> TCPIP HELP
Chapter 2. Tuning Techniques
This chapter describes how to change system operation to solve specific networking problems. Once you have diagnosed the cause of the problem, as described in Chapter 1, use the information in this chapter to solve the problem.
The tuning techniques described in this chapter include:
Modifying subsystem attributes (Section 2.1)
Tuning server applications (Section 2.2.2)
Solving server performance problems (Section 2.3)
2.1. Subsystem Attributes
TCP/IP Services supports UNIX subsystems and allows you to modify the attributes of those subsystems to change the way the TCP/IP Services software operates.
Subsystem configuration is provided for compatibility with UNIX systems. VSI strongly advises you not to modify the attributes associated with subsystems except when the adjustment of an attribute is indicated (for example, to improve performance). In most cases, corresponding TCP/IP management commands are provided to help limit the side effects of modifying subsystem attributes.
The following sections describe how to display and modify the settings of the subsystem attributes. Modifying subsystem attributes without full knowledge of possible effects can cause unpredictable results and is recommended only as specifically directed by VSI.
2.1.1. Displaying Subsystems and Attributes
$ TCPIP TCPIP> sysconfig -s cm: loaded and configured inet: loaded and configured iptunnel: loaded and configured ipv6: loaded and configured net: loaded and configured snmpinfo: loaded and configured socket: loaded and configured inetkvci: loaded and configured proxy: loaded and configured nfs: loaded and configured vfs: loaded and configured TCPIP>
Note
Depending on the configuration of your system, the list of subsystems displayed may differ from this example.
2.1.1.1. Static and Dynamic Subsystems
There are two types of subsystems:
Static subsystems are loaded at startup time and can be unloaded only when TCP/IP shuts down.
Dynamic subsystems can be loaded and unloaded at will without shutting down and restarting TCP/IP Services.
sysconfig -m command to display static and
dynamic subsystems, as
follows:$ TCPIP TCPIP> sysconfig -m cm: static inet: static iptunnel: static ipv6: static net: static snmpinfo: static socket: static inetkvci: static proxy: static nfs: static vfs: static
Subsystems can be loaded but not available for use. Subsystems can have the following states:
Loaded and configured (available for use)
Loaded and unconfigured (not available for use)
This state applies only to static subsystems, which you can unconfigure, but you cannot unload.
Unloaded (not available for use)
This state applies only to loadable subsystems, which are automatically unloaded when you unconfigure them.
2.1.1.2. Displaying the Attribute Values for a Subsystem
Each subsystem contains a set of attributes with associated values.
-q option and the name of the subsystem. For example, to
display the attributes of the socket subsystem, enter the following
command:TCPIP> sysconfig -q socket socket: sbcompress_threshold = 0 sb_max = 1048576 sobacklog_drops = 0 sobacklog_hiwat = 1 soinp_reuse = 1 somaxconn = 1024 somaxconn_drops = 0 sominconn = 1 TCPIP>
Subsystem attributes are specific to OpenVMS. Some UNIX attributes area not supported on OpenVMS systems.
To determine whether an attribute is supported, use the -q option and specify both the subsystem and the attribute.
TCPIP> sysconfig -q inet tcbhashsize framework error: subsystem 'inet' not found
To display the maximum and minimum values for attributes, include the -Q option and specify both the subsystem and the attribute. If you do not specify an attribute, the system displays all the attributes for the specified subsystem.
Note
On OpenVMS, you must enclose any uppercase options in quotation marks.
rexmtmax attribute in the inet subsystem, enter the following
command:TCPIP> sysconfig "-Q" inet tcp_rexmtmax inet: tcp_rexmtmax - type=INT op=CRQ min_val=1 max_val=2147483647 TCPIP>
The sysconfig "-Q" command also displays the op code, which can
consist of one or more of the following:
C, which indicates that the attribute can be configured
R, which indicates that the attribute can be reconfigured
Q, which indicates that the attribute can be queried
2.1.2. Modifying Subsystem Attribute Values
You can modify the values of subsystem attributes either temporarily or permanently.
If you change the value of a subsystem attribute at run time, the change will persist only as long as the system continues to run. When you reboot the system, the attribute value reverts to the previous setting.
For temporary modifications that will not persist across reboots, use the
sysconfig -r command as described in Section 2.1.2.1.
To modify an attribute value permanently, include the attribute in the system configuration table, sysconfigtab. Values specified in sysconfigtab are preserved through system reboots. To include an attribute in the sysconfigtab file, use the sysconfigdb utility, as described in Section 2.1.3.
Note
Always use the recommended utility to modify subsystem attributes. Do not
modify the sysconfigtab file directly.
2.1.2.1. Reconfiguring Attributes
You can reconfigure an attribute (that is, modify its value temporarily),
using the sysconfig command, if the attribute is reconfigurable
(the op code includes R). This allows you to determine whether
modifying an attribute will improve your system performance. Temporary
modifications are lost when you reboot the system.
To temporarily modify an attribute's current value, use the
sysconfig command with the -r option. Specify both
the subsystem and the attribute on the command line:
tcp_keepinit value to be 30
temporarily, enter the following
command:TCPIP> sysconfig -r inet tcp_keepinit=30 tcp_keepinit: reconfigured TCPIP>
After modifying the attribute value, you must either reload the subsystem or restart TCP/IP Services, depending on whether the attribute is part of a dynamic subsystem or a static subsystem.
Unload the dynamic subsystem using the
sysconfig -ucommand. Then use thesysconfig -rcommand to reload the subsystem.Reload static subsystems by stopping and restarting TCP/IP Services.
2.1.3. Configuring Attributes
You can configure an attribute (that is, modify subsystem attributes so that changes persist across reboots), by storing the attribute and its value in the system configuration table (TCPIP$ETC:SYSCONFIGTAB.DAT), if the attribute's op code includes C.
When a subsystem is loaded, the attributes that are not listed in the SYSCONFIGTAB.DAT file are set to their default values.
To modify subsystem attributes in the SYSCONFIGTAB.DAT file, follow these steps:
Use the
sysconfigdbutility to update the system configuration table, as described in Section 2.1.3.1Reload the subsystem. A dynamic subsystem can be unloaded and reloaded using the
sysconfigutility. A static subsystem is reloaded when the TCP/IP Services software is restarted.
2.1.3.1. Format of the SYSCONFIGTAB File
The TCPIP$ETC:SYSCONFIGTAB.DAT file is an ASCII text file in stanza file
format. Do not edit the sysconfigtab file directly. Always use the
recommended commands to modify attribute values in the sysconfigtab
file.
sysconfigtab file is formatted as
follows:subsystem1:
parameter1=value1 parameter1=value2
subsystem2:
parameter1=value1 parameter1=value2$ TYPE SOCKET_ATTRS.TXT
socket:
socket_param1 = socket_value1
$After you create the stanza file, update the system configuration table using
the sysconfigdb utility.
sysconfigdb utility, enter the following
commands:$ TCPIP TCPIP> sysconfigdb
sysconfigdb
command with the -u option. Specify the stanza file on the command
line using the -f option. The following is the format of the
sysconfigdb
command:TCPIP> sysconfigdb -u -f stanza-filename subsystem
In this command line, stanza-filename is the file name of the stanza file that you created. The value for subsystem is the subsystem name for which you are changing an attribute.
The sysconfigdb command reads the specified file and updates the
sysconfigtab file. The modifications are made to the subsystem
when it is reloaded.
$ TYPE TABLE_MGR.STANZA
table_mgr_1:
size = 10
name = Ten-Element-Table
tbl_mgr_2:
size = 5
name = Five-Element-Table
$ $ TCPIP TCPIP> sysconfigdb -a -f table_mgr.stanza table_mgr_1 TCPIP> sysconfigdb -a -f table_mgr.stanza tbl_mgr_2
This example does not change the value of attributes on the running system. For information about changing attribute values on the running system, see Section 2.1.2.1.
For complete information about using the sysconfigdb command,
refer to Appendix A.
2.1.3.2. Stanza File Format
entry-name:
Attribute1-name = Attribute1-value
Attribute2-name = Attribute2-value
Attribute3-name = Attribute3-value1, Attribute3-value2
.
.
.The entry-name variable specifies the subsystem name.
The attributes for the subsystem are specified with the Attribute1-name, Attribute2-name, and Attribute3-name variables.
The values for the attributes are specified with the Attribute1-value, Attribute2-value, Attribute3-value1, and Attribute3-value2 variables.
The stanza file syntax rules are as follows:
Separate entries by one or more blank lines.
A colon (:) terminates an entry name.
A new line terminates an attribute name and value pair.
Separate a attribute name and attribute value with an equals sign (=).
Separate more than one attribute value with a comma (,).
Entry names and attribute names can contain any printable character except spaces, new lines, and special characters, which must be specified appropriately.
Entry attribute values can contain any printable character except new lines and special characters, which must be specified appropriately.
Spaces and tabs are allowed at the beginning and at the end of lines.
A pound sign (#) at the beginning of a line indicates a comment.
Comments should be included only at the beginning or the end of an entry.
\007
2.1.4. Modifying Kernel Subsystems
Most resources used by the network subsystem are allocated and adjusted dynamically. However, you can make some adjustments to improve performance.
Table 2.1 summarizes the adjustments you can make, lists performance benefits and the adjustments that will achieve them, along with the tradeoffs (where applicable) associated with each adjustment.
|
Performance Benefit |
Tuning Adjustment |
Tradeoff |
|---|---|---|
|
Reduce the number of dropped incoming connection requests. |
Increase the maximum number of pending TCP connections (Section 2.1.5.1). |
Consumes memory resources. |
|
Allow each server socket to handle more SYN packets simultaneously. |
Increase the minimum number of pending TCP connections (Section 2.1.5.2). |
Consumes memory resources. |
|
Allow for a larger socket buffer. |
Increase the maximum socket buffer size (Section 2.1.5.3). |
Consumes memory. If you have a large number of sockets, memory consumption could be of concern. |
|
Improve the TCP control block lookup rate and increase the raw connection rate. |
Increase the size of the hash table that the kernel uses to look up TCP control blocks (Section 2.1.6.1). |
Slightly increases the amount of pooled memory. |
|
Reduce hash table lock contention for SMP systems. |
Increase the number of TCP hash tables (Section 2.1.6.2). |
Slightly increases the amount of pooled memory. |
|
Improve performance on systems that use large numbers of interface alias. |
Increase the size of the kernel interface alias table (Section 2.1.6.3). |
None. |
|
Allow partial connections to time out sooner, preventing the socket listen queue from filling up with SYN packets. |
Increase the TCP partial connection timeout rate (Section 2.1.6.4). |
Setting the
tcp_keepinitvalue too low can cause connections to be broken prematurely. |
|
Prevent premature retransmissions and decrease congestion. |
Reduce the TCP retransmission rate (Section 2.1.6.5). |
A long retransmit time is not appropriate for all configurations. |
|
Clean up sockets that do not exit cleanly when the
|
None. | |
|
Free connection resources sooner. |
Make the TCP connection context time out more quickly at the end of the connection (Section 2.1.6.7). |
Reducing the timeout limit increases the potential for data corruption; use caution if you make this adjustment. |
|
Provide TCP and UDP applications with a specific range of ports. |
Modify the range of outgoing connection ports (Section 2.1.6.9). |
None. |
|
Improve the efficiency of servers that handle remote traffic from many clients. |
Disable the use of a PMTU (Section 2.1.6.10). |
May reduce server efficiency for LAN traffic. |
|
Allow large socket buffer sizes. |
Increase the maximum size of a socket buffer (Section 2.1.5.3). |
Consumes memory resources. |
|
Improve handling of a large number of BG devices. |
Enable fast device creation and deletion (Section 2.2.4). |
Consumes memory resources. |
The following sections describe in detail how to modify socket and
inet subsystem attributes.
2.1.5. Modifying Socket Subsystem Attributes
socket subsystem attributes control the maximum number of pending
connection attempts per server socket (that is, the maximum depth of the listen or
SYN queue) and other behavior. You may be able to improve server performance by
modifying the socket subsystem attributes described in Table 2.2.socket Subsystem Attributes|
Attribute |
Description |
|---|---|
|
|
Controls the maximum number of pending TCP connections. |
|
|
Controls the minimum number of pending TCP connections. |
|
|
Controls the maximum size of a socket buffer. |
In addition, the socket subsystem attributes
sobacklog_hiwat, sobacklog_drops, and
somaxconn_drops track events related to socket listen queues. By
monitoring these attributes, you can determine whether the queues are overflowing.
2.1.5.1. Increasing the Maximum Number of Pending TCP Connections
The socket subsystem attribute somaxconn specifies
the maximum number of pending TCP connections (the socket listen queue limit)
for each server socket (for example, for the HTTP server socket). Busy servers
often experience large numbers of pending connections. If the listen queue
connection limit is too small, incoming connection requests may be dropped.
Pending TCP connections can be caused by lost packets in the internet or denial
of service attacks.
The default value for somaxconn is 1024.
VSI recommends increasing the somaxconn attribute to the maximum
value, except on low-memory systems. The maximum value is 65535. Specifying a
value that is higher than the maximum value can cause unpredictable behavior.
2.1.5.2. Increasing the Minimum Number of Pending TCP Connections
The socket subsystem attribute sominconn specifies
the minimum number of pending TCP connections (backlog) for each server socket.
This attribute controls how many SYN packets can be handled simultaneously
before additional requests are discarded. Network performance can degrade if a
client saturates a socket listen queue with erroneous TCP SYN packets,
effectively blocking other users from the queue.
The value of the sominconn attribute overrides the
application-specific backlog value, which may be set too low for some server
software. If you do not have your application source code, you can use the
sominconn attribute to set a sufficient pending-connection
quota.
The default value is 0.
VSI recommends increasing the value of the sominconn attribute to
the maximum value of 65535. The value of the sominconn attribute
should be the same as the value of the somaxconn attribute (see
Section 2.1.5.1).
2.1.5.3. Increasing the Maximum Size of a Socket Buffer
The socket subsystem attribute sb_max specifies the
maximum size of a socket buffer.
Performance Benefits and Tradeoffs
Increasing the maximum size of a socket buffer may improve performance if your applications can benefit from a large buffer size.
You can modify the sb_max attribute without rebooting the system.
When to Tune
If you require a large socket buffer, increase the maximum socket buffer size.
Recommended Values
The default value of the sb_max attribute is 128 KB. Increase
this value before you increase the size of the transmit and receive socket
buffers.
2.1.6. Modifying Internet Subsystem Attributes
inet subsystem performance by modifying
the attributes described in Table 2.3.inet Subsystem Attributes|
Attribute |
Description |
|---|---|
|
|
Controls the size of a TCP hash table. |
|
|
Specifies the number of TCP hash tables. |
|
|
Controls the size of the kernel interface alias table. |
|
|
Specifies the TCP partial connection timeout rate. |
|
|
Specifies the rate of TCP retransmissions. |
|
|
Enables or disables the TCP keepalive function. |
|
|
Specifies the TCP connection context timeout rate. |
|
|
Delays acknowledgment messages after the receipt of network frames. |
|
|
Specifies the maximum value for the range of outgoing connection ports. |
|
|
Specifies the minimum value for the range of outgoing connection ports. |
|
|
Enables or disables use of the PMTU protocol. |
|
|
Prevents dropped input packets. |
2.1.6.1. Increasing the Size of a TCP Hash Table
You can modify the size of the hash table that the kernel uses to look up
Transmission Control Protocol (TCP) control blocks. The inet
subsystem attribute tcbhashsize specifies the number of hash
buckets in the kernel TCP connection table (the number of buckets in the
inpcb hashtable).
Performance Benefits and Tradeoffs
The kernel must look up the connection block for every TCP packet it receives, so increasing the size of the table can speed the search and improve performance. This results in a small increase in pooled memory.
You can modify the tcbhashsize attribute without rebooting the
system.
When to Tune
Increase the number of hash buckets in the kernel TCP connection table if you have an server.
Recommended Values
The default value of the tcbhashsize attribute is 512. For
Internet servers, set the tcbhashsize attribute to 16384.
2.1.6.2. Increasing the Number of TCP Hash Tables
You can increase the number of hash tables the kernel uses to look up TCP
control blocks. Because the kernel must look up the connection block for every
Transmission Control Protocol (TCP) packet it receives, a bottleneck may occur
at the TCP hash table in SMP systems. Increasing the number of tables
distributes the load and may improve performance. The inet
subsystem attribute tcbhashnum specifies the number of TCP hash
tables.
Performance Benefits and Tradeoffs
For SMP systems, you may be able to reduce hash table lock contention by increasing the number of hash tables that the kernel uses to look up TCP control blocks. This will slightly increase pooled memory.
You cannot modify the tcbhashnum attribute without rebooting the
system.
When to Tune
Increase the number of TCP hash tables if you have an SMP system that is an server.
Recommended Values
The minimum value of the tcbhashnum attribute is 1 (the default).
The maximum value is 64. For busy server SMP systems, you can increase the value
of the tcbhashnum attribute to 16. If you increase this attribute,
you should also increase the size of the hash table by a similar factor. See
Section 2.1.6.1 for more information.
2.1.6.3. Increasing the Size of the Kernel Interface Alias Table
The inet subsystem attribute inifaddr_hsize
specifies the number of hash buckets in the kernel interface alias table
(in_ifaddr).
If a system is used as a server for many different server domain names, each of which is bound to a unique IP address, the code that matches arriving packets to the right server address uses the hash table to speed lookup operations for the IP addresses.
Performance Benefits and Tradeoffs
Increasing the number of hash buckets in the table can improve performance on systems that use large numbers of aliases.
When to Tune
Increase the number of hash buckets in the kernel interface alias table if your system uses large numbers of aliases.
You can modify the inifaddr_hsize attribute without rebooting the
system.
Recommended Values
The default value of the inet subsystem attribute
inifaddr_hsize is 32; the maximum value is 512.
For the best performance, the value of the inifaddr_hsize
attribute is always rounded down to the nearest power of 2. If you are using
more than 500 interface IP aliases, specify the maximum value of 512. If you are
using fewer than 250 aliases, use the default value of 32. For a number of
aliases between 250 and 500, use a value that is a power of 2 between 32 and
512.
2.1.6.4. Increasing the TCP Partial Connection Timeout Rate
If increasing the somaxconn limit does not prevent the listen
queue from filling, or if the default grows to an excessive length, you can make
partial connections time out sooner by decreasing the value of the
inet subsystem attribute tcp_keepinit.
The tcp_keepinit attribute specifies the amount of time that a
partial connection remains on the socket listen queue before it times out.
Performance Benefits and Tradeoffs
Network performance can degrade if a client overfills a socket listen queue
with TCP SYN packets, thereby blocking other users from the queue. To eliminate
this problem, increase the value of the sominconn attribute to its
maximum value. If the system continues to drop SYN packets, decrease the value
of the tcp_keepinit attribute to 30 (15 seconds). Monitor the
values of the sobacklog_drops and somaxconn_drops
attributes to determine whether the system is dropping packets. (See Section 2.1.7 for more information about event
counters.)
You can modify the tcp_keepinit attribute without rebooting the
system.
When to Tune
Modify the TCP partial-connection timeout limit only if the value of the
somaxconn_drops attribute increases often. If this occurs,
decrease the value of the tcp_keepinit attribute.
Recommended Values
The value of the tcp_keepinit attribute is in units of 0.5
seconds. The default value is 150 units (75 seconds). If the value of the
sominconn attribute is 65535, use the default value of the
tcp_keepinit attribute.
If you set the value of the tcp_keepinit attribute too low, you
may prematurely break connections associated with clients on network paths that
are slow or network paths that lose many packets. Do not set the value to less
than 20 units (10 seconds).
2.1.6.5. Slowing TCP Retransmission Rate
The inet subsystem attribute tcp_rexmit_interval_min
specifies the minimum amount of time before the first TCP retransmission.
Performance Benefits and Tradeoffs
You can increase the value of the tcp_rexmit_interval_min
attribute to slow the rate of TCP retransmissions, which decreases congestion
and improves performance.
You can modify the tcp_rexmit_interval_min attribute without
rebooting the system.
When to Tune
Not every connection needs a long retransmission time. Usually, the default value is adequate. However, for some wide area networks (WANs), the default retransmission interval may be too small, causing premature retransmission timeouts. This may lead to duplicate transmission of packets and the erroneous invocation of the TCP congestion-control algorithms.
To check for retransmissions, use the netstat -p tcp command and
examine the output for data packets retransmitted.
Recommended Values
The tcp_rexmit_interval_min attribute is specified in units of
0.5 second. The default value is 2 units (1 second).
Do not specify a value that is less than 1 unit. Do not change the attribute unless you fully understand TCP algorithms and your network topology.
2.1.6.6. Enabling the TCP Keepalive Function
The keepalive function enables the periodic transmission of messages on a connected socket in order to keep connections active. Sockets that do not exit cleanly are cleaned up when the keepalive interval expires. If keepalive is not enabled, those sockets continue to exist until you reboot the system.
setsockopt function's
SO_KEEPALIVE
keepalive, or if you do not
have access to the application sources, use the inet subsystem
attribute tcp_keepalive_default to enable keepalive
functionality.Performance Benefit
Keepalive functionality cleans up sockets that do not exit cleanly when the keepalive interval expires.
You can modify the tcp_keepalive_default attribute without
rebooting the system. However, sockets that already exist will continue to use
old behavior, until the applications are restarted.
When to Tune
Enable keepalive if you require this functionality, and you do not have access to the source code.
Recommended Values
To override programs that do not set keepalive, or if you do not have access
to application source code, set the inet subsystem attribute
tcp_keepalive_default to 1 in order to enable keepalive for all
sockets.
|
Option |
Description |
|---|---|
|
| Specifies the amount of idle time, in seconds, before sending a keepalive probe. The default interval is two hours. |
|
| Specifies the amount of time, in seconds, between retransmission of keepalive probes. The default interval is 75 seconds. |
|
| Specifies the maximum number of keepalive probes that are sent before the connection is dropped. The default is 8 probes. |
|
| Specifies the maximum amount of time, in seconds, before an initial connection attempt times out. The default is 75 seconds. |
2.1.6.7. Increasing the Timeout Rate for TCP Connection Context
The TCP protocol includes a concept known as the Maximum Segment Lifetime
(MSL). When a TCP connection enters the TIME_WAIT state, it must
remain in this state for twice the value of the MSL; otherwise, undetected data
errors on future connections can occur. The inet subsystem
attribute tcp_msl determines the maximum lifetime of a TCP segment
and the timeout value for the TIME_WAIT state.
In some situations, the default timeout value for the TIME_WAIT
state (60 seconds) is too large, thereby reducing the value of the
tcp_msl attribute frees connection resources sooner than the
default setting.
Performance Benefits and Tradeoffs
You can decrease the value of the tcp_msl attribute to make the
TCP connection context time out more quickly at the end of a connection.
However, this will increase the chance of data corruption.
You can modify the tcp_msl attribute without rebooting the
system.
When to Tune
Usually, you do not have to modify the timeout limit for the TCP connection context.
Recommended Values
The value of the tcp_msl attribute is set in units of 0.5 second.
The default value is 60 units (30 seconds), which means that the TCP connection
remains in TIME_WAIT state for 60 seconds, or twice the value of the MSL.
Do not reduce the value of the tcp_msl attribute unless you fully
understand the design and behavior of your network and the TCP protocol. It is
strongly recommended that you use the default value; otherwise, there is the
potential for data corruption.
2.1.6.8. Disabling Delayed Acknowledgment
The TCP/IP software can send an acknowledgment packet for every frame received over the network. However, this is an inefficient mode of operation. The tcp_nodelack attribute controls the delay of acknowledgment messages.
When this attribute is set to 0 (the default), network traffic is greatly reduced. If you set this attribute to 1, an acknowledgment message is sent for every frame received, increasing network traffic and impacting the performance of the network server.
2.1.6.9. Modifying the Range of Outgoing Connection Ports
When a TCP or UDP application creates an outgoing connection, the kernel
dynamically allocates a nonreserved port number for each connection. The kernel
selects the port number from a range of values between the value of the
inet subsystem attribute ipport_userreserved_min
and the value of the ipport_userreserved attribute. Using the
default values for these attributes, the range of outgoing ports starts at 49152
and stops at 65535.
Performance Benefits and Tradeoffs
Modifying the range of outgoing connections provides TCP and UDP applications with a specific range of ports.
You can modify the ipport_userreserved_min and
ipport_userreserved attributes without rebooting the
system.
When to Tune
If your system requires outgoing ports from a particular range, you can modify
the values of the ipport_userreserved_min and
ipport_userreserved attributes.
Recommended Values
The default value of the ipport_userreserved_min attribute is
49152. The default value of the ipport_userreserved is 65535. The
maximum value of each attribute is 65535.
Do not reduce the ipport_userreserved attribute to a value that
is less than 65535, and do not reduce the ipport_userreserved_min
attribute to a value that is less than 49152.
2.1.6.10. Disabling Use of the PMTU Protocol
Packets transmitted between servers are fragmented into units of a specific
size in order to ease transmission of the data over routers and small-packet
networks, such as Ethernet networks. When the inet subsystem
attribute pmtu_enabled is enabled (set to 1, which is the default
behavior), the system determines the largest common path maximum transmission
unit (PMTU) value between servers and uses it as the unit size. The system also
creates a routing table entry for each client network that attempts to connect
to the server.
Performance Benefits and Tradeoffs
If a server handles traffic among many remote clients, disabling the use of a PMTU can decrease the size of the kernel routing table, which improves server efficiency. However, on a server that handles local traffic and some remote traffic, disabling the use of a PMTU can degrade bandwidth.
When to Tune
If an server has poor performance and the routing table increases to more than 1000 entries, you should disable the use of PMTU. This is also recommended if you have a server that handles traffic among many remote clients.
Recommended Values
To disable the use of PMTU protocol, set the value of the
pmtu_enabled attribute to 0.
2.1.7. Displaying Socket Statistics
socket subsystem has three attributes that monitor socket listen
queue events: The
sobacklog_hiwatattribute counts the maximum number of pending requests to any server socket.The
sobacklog_dropsattribute counts the number of times the system dropped a received SYN packet because the number of queued SYN_RCVD connections for a socket equaled the socket's backlog limit.The
somaxconn_dropsattribute counts the number of times the system dropped a received SYN packet because the number of queued SYN_RCVD connections for the socket equaled the upper limit on the backlog length (somaxconnattribute).
sysconfig -q socket
The value of the sominconn attribute should equal the value of the
somaxconn attribute. When these two attributes are equal, the value
of somaxconn_drops will have the same value as
sobacklog_drops.
However, if the value of the sominconn attribute is 0 (the default),
and if one or more server applications uses an inadequate value for the backlog
argument to its listen system call, the value of sobacklog_drops may
increase at a rate that is faster than the rate at which the
somaxconn_drops counter increases. If this occurs, you may want to
increase the value of the sominconn attribute. See Section 2.1.5.2 for more information.
2.2. Tuning Server Applications
In addition to tuning TCP/IP Services kernel attributes, performance improvements can be made to server applications by:
Ensuring adequate memory configuration
Logging IP addresses
2.2.1. Configuring Memory for High Performance
Kernel socket structure
Internet protocol control block (
inpcb) structureTCP control block structure
Any socket buffer space that is needed as packets arrive and are consumed
These memory resources total 1 KB for each connection endpoint (not including the socket buffer space), which means 10 MB of memory is required in order to accommodate 10,000 connections.
Your server must have enough memory to handle demanding peak loads. As a rule of thumb, if you configure ten times more memory than the server requires on a busy day, you will have sufficient memory to handle occasional spikes of activity.
There are no limitations on a server's ability to handle millions of TCP
connections if memory resources are available to service the connections. If memory
is insufficient, the server will reject new connection requests until memory is
available. Use the netstat -m command to monitor the memory that is
currently being used by the network subsystem. See Section 1.2.4
for information about displaying memory statistics.
2.2.2. Logging IP Addresses
If your server application logs client host names, the application software may force the system to perform a reverse DNS lookup to obtain the client's host name. Reverse DNS lookups are time-intensive and can cause performance problems on servers with many clients.
Many applications can be modified to log client IP addresses instead of client host names. Logging IP addresses instead of host names may significantly improve the efficiency of the server. Consult the documentation provided by the server software vendor to determine how to disable the logging of client host names.
For example, you can obtain information about modifying Apache HTTP Server software from the Apache HTTP Server documentation site.
2.2.3. Increasing the Auxiliary Server Connection Limit
The auxiliary server handles a limited number of service invocations in a one-minute period of time. The default is a maximum of 500 connection requests. If the number of requests exceeds this limit, the auxiliary server will not accept additional requests for that service.
If your server receives more than eight requests per second for a service that is spawned by the auxiliary server (for example, POP-3, FTP, and SMTP servers), increase the default connection request limit. You can check the service's log file to determine if a service has been shut down. For example, the file SYS$SYSDEVICE:[TCPIP$POP]TCPIP$POP_RUN.LOG will contain information about the POP service.
Because the auxiliary server does not spawn any known HTTP server, the connection request limit does not affect HTTP service.
2.2.4. Increasing the Maximum Number of BG Devices
You can configure TCP/IP Services to create more than 10,000 devices. This is useful if the system is a web server.
net Subsystem Attributes | Attribute | Description |
|
| Informational attribute that shows the number of BG devices that exist in the system. You cannot modify this attribute. |
|
| Information attribute that shows a running total of all the BG devices created since TCP/IP Services was started. You can use this information to see how often devices are being used. You cannot modify this attribute. |
|
|
Specifies fast creation and deletion of BG devices, useful
on a system that uses many BG devices. Modifying this
attribute can improve performance by reducing:
The default setting for this attribute is 0, or OFF. This attribute can affect the amount of virtual memory used. To calculate the effect of this attribute on virtual memory usage, add one to the the number of BG devices (ovms_unit_maximum ) and multiply by 4. For example, with the default setting of 9999, the virtual memory is 40,000 bytes. At its maximum value of 32767, the virtual memory is 131,072 bytes. You can modify this attribute. |
|
| This informational attribute shows the calculated maximum number of concurrent BG device units that can coexist at any time given the values of the ovms_unit_maximum and ovms_unit_minimum attributes. Note that BG0 and BG1 are always reserved. You cannot modify this attribute. |
|
| Specifies the lowest numbered device unit. All BG devices after BG0 will begin with this unit number. You can modify this attribute. |
|
| Specifies the highest numbered device unit. It is possible there will be BG device numbers above this, but they are not available to users. You can specify a value from 9999 to 32767. You can modify this attribute. |
|
| This informational attribute shows the next BG unit number that will be created. If ovms_unit_fast_credel is enabled, a duplicate BG device unit is sensed immediately and the unit seed incremented. If ovms_unit_fast_credel is not enabled, a device scan will occur as it normally does with cloned devices. |
2.3. Solving Performance Problems
This section contains information that you can use to identify and solve server performance problems.
Monitor the server.
See Section 1.2.4 for information about monitoring the network, the virtual memory subsystem, and network socket statistics.
Apply any patches recommended for your operating system.
See the Recommended Patch Table for information about operating system patches that can improve performance.
Apply the kernel attribute values that are recommended for your type of system.
See Section 2.3.1 for a list of attributes that can be tuned to improve performance.
Prevent “forbidden” and “url could not load” messages on Netscape enterprise server systems.
2.3.1. Tuning Recommendations for a Primary Server
This section provides recommendations for tuning a server for optimal performance. These recommendations are applicable to most configurations and include the attribute value and a reference to additional information.
- Tune the following
socketsubsystem attributes:somaxconn = 65535 sominconn = 65535 - Tune the following
inetsubsystem attributes:pmtu_enabled = 0
- Modify the following socket subsystem attribute as follows:
sbcompress_threshold = 600
- Modify the following
inetsubsystem attribute as follows:ipport_userreserved = 65000
2.3.2. Improving Gigabit Ethernet Performance
You can improve the performance of TCP/IP Services over Gigabit Ethernet (GbE) by configuring the system to use jumbo frames.
Jumbo frames (frames larger than the 1518 octets specified by the IEEE 802.3 standard) improve performance because more data can be transmitted in each frame, hence reducing the frame rate and interrupt load on a system. Jumbo frames must be configured on both the Gigabit Ethernet switch as well as the Gigabit Ethernet controllers on the host systems. Configure jumbo frames before you start TCP/IP Services on the OpenVMS server.
There are two ways to configure jumbo frames for Gigabit Ethernet controllers on OpenVMS:
- Including the following LANCP command in SYSTARTUP_VMS.COM:
$ mcr lancp set dev ewa/jumbo ! enable jumbo frames for GbE.
- Setting the SYSGEN parameter LAN_FLAGS in MODPARAMS.DAT and running AUTOGEN. For example:
LAN_FLAGS=64 ! Set bit 6 to enable jumbo frames on GbE, a dynamic parameter
Restart TCP/IP Services after you enable jumbo frames dynamically.
$ ifconfig we0
WE0: flags=c43<UP,BROADCAST,RUNNING,MULTICAST,SIMPLEX>
*inet 10.0.0.4 netmask ffff0000 broadcast 10.0.255.255 ipmtu 9000 You can verify jumbo frame configuration using the tcpdump command. For example, consider two systems connected with Gigabit Ethernet, GIGA1 and GIGA2:
$ tcpdump -c 2 -t port telnet
$ TELNET giga1
tcpdump command displays the two packets from the TCP connection
establishment and reveals the negotiated maximum segment size (mss).
For example, on a correctly configured system the tcpdump trace from the TELNET
command
shows:$ tcpdump -c 2 -t port telnet tcpdump: listening on Filtering in user process GIGA2.49188 > GIGA1.23: S 165176320:165176320(0) win 3000 <mss 8960,nop,wscale 0> GIGA1.23 > GIGA2.49188: S 1890602256:1890602256(0) ack 165176321 win 3000 <mss 8960,nop,wscale 0> 2 packets (out of 5 examined)
Note that the requested mss of 8960 in the SYN packet is also accepted by the server in the SYN ACK packket. On earlier versions of OpenVMS, the jumbo-frame mss may be less than 8960 bytes.
$ tcpdump -c 2 -t port telnet tcpdump: listening on Filtering in user process GIGA2.49187 > GIGA1.23: S 142920192:142920192(0) win 3000 <mss 8960,nop,wscale 0> GIGA1.23 > GIGA2.49187: S 2953104448:2953104448(0) ack 142920193 win 4380 <mss 1460,nop,wscale 0> 2 packets (out of 5 examined)
The TELNET client requests an mss of 8960 bytes in the SYN packet, but the server responds with an mss of 1460 bytes in the SYN ACK packet. Therefore, GIGA1 is not correctly configured for jumbo frames.
Appendix A. Troubleshooting Utilities Reference
This appendix provides more information about the troubleshooting utilities described in this manual. It also describes the utilities used for isolating and resolving problems with your network and network software.
To invoke a utility as a command at the system prompt, execute the SYS$STARTUP:TCPIP$DEFINE_COMMANDS.COM file. Execution of this file defines each utility as a foreign command.
arp
arp — Displays and controls Address Resolution Protocol (ARP) tables.
Syntax
arp [-u] [-n] hostname
arp -a [-u] [-n] [-i] hostname
arp -d hostname
arp -g hostname
arp -s [-u] hostname hardware_addr [temp] [pub]
[trail]
arp -f filename
Description
The arp command displays or modifies the current ARP entry for the
host specified by hostname. The hostname
value can be specified by name or IP address, using dotted-decimal notation.
With no flags, the program displays the current ARP entry for
hostname.
The ARP tables can be displayed by any user, but only privileged users can modify them.
Flags
- -a
Displays all current ARP entries.
- -d hostname
Deletes the entry for hostname if the user entering the command is a privileged user.
- -f filename
- Reads entries from filename and adds those entries to the ARP tables. Use of this flag requires system privileges. Entries in the file have the following format:
hostname hardware_addr [temp] [pub] [trail]Fields in this format are:Option
Description
hostname
Specifies the remote host identified by the entry.
hardware_addr
Specifies the hardware address of the remote host. The address is given as 6 hexadecimal bytes separated by colons.
tempSpecifies that this ARP table entry is temporary. When this argument is not used, the table entry is permanent.
pubIndicates that the table entry will be published and that the current system will act as an ARP server, responding to requests for hostname even though the host address is not its own.
trailIndicates that the trailer encapsulation can be sent to this host.
- -g hostname
Sends a gratuitous ARP packet. The value for hostname can be a local host name, alias, or IP address.
- -i hostname
Displays the interface with which the ARP entry is associated.
- -n hostname
Displays numeric IP addresses and hardware addresses only. When this flag is not specified, arp displays hostnames, numeric IP addresses, and hardware addresses.
- -s hostname hardware_addr [temp] [pub]
- Creates a single ARP entry for hostname. Use of this flag requires privileges. Fields in the format are:
hostname
Specifies the remote host identified by the entry.
hardware_addr
Specifies the hardware address of the remote given as 6 hexadecimal bytes separated by colons.
tempSpecifies that this ARP table entry is temporary. When this argument is not used, the table entry is permanent.
pubIndicates that the table entry will be published and the current system will act as an ARP server, responding to requests for
hostnameeven though the host address is not its own. - -u
Displays the MAC address in noncanonical form, with address bytes reversed and separated by a colon character (:). By default, all addresses are displayed in canonical form with address bytes separated by the hyphen character (-).
When used with the
-sflag, this indicates the hardware_addr is specified in noncanonical form.
Examples
The following examples show how to use the arp command.
TCPIP> arp -a a71kt.lkg.dec.com (10.10.2.1) at aa-00-04-00-71-f8 stale v71kt.lkg.dec.com (10.10.2.3) at aa-00-04-00-70-f8 stale v72kt.lkg.dec.com (10.10.2.4) at aa-00-04-00-6d-f8 tlab9.lkg.dec.com (10.10.2.11) at aa-00-04-00-42-11 timber.lkg.dec.com (10.10.2.14) at aa-00-04-00-c9-f8
This example shows how to display the ARP address-mapping tables for the local host.
TCPIP> arp -a -i a71kt.lkg.dec.com (10.10.2.1) at aa-00-04-00-71-f8 stale (WE0) v71kt.lkg.dec.com (10.10.2.3) at aa-00-04-00-70-f8 (WE0) v72kt.lkg.dec.com (10.10.2.4) at aa-00-04-00-6d-f8 stale (WE0) tlab9.lkg.dec.com (10.10.2.11) at aa-00-04-00-42-11 (WE0) timber.lkg.dec.com (10.10.2.14) at aa-00-04-00-c9-f8 (WE0)
This example shows how to display the ARP address-mapping tables for the local host and the interface.
TCPIP> arp -s laszlo 08:00:2b:0f:44:23 temp
This example shows how to add a single entry for the remote host
laszloto the ARP mapping tables temporarily. The address is considered canonical even though the bytes are separated by colons. For input, thearpcommand does not use the colon (:) and hyphen (-) characters to indicate whether the address is canonical or noncanonical. You must have system privileges to execute this command.TCPIP> arp -u -s laszlo 10:00:d4:f0:22:c4 temp
This example shows how to add a single entry for the remote host
laszloto thearpmapping tables temporarily. The-uflag indicates the address is noncanonical. You must have system privileges to execute this command.TCPIP> arp -f newentries
This example shows how to add multiple entries to the ARP mapping tables from a file named
newentries. You must have system privileges to execute this command.
dig
dig — Sends domain name query packets to name servers.
Syntax
dig [@server]
domain[query-type]
[query-class] [+query-option]
[-dig-option]
[%comment]
Description
Domain Information Groper ( dig ) is a flexible command line utility
you can use to gather information from Domain Name System servers. The
dig utility has two modes: simple interactive mode, which makes a
single query; and batch mode, which executes a query for each query in a list of
several query lines. All query options are accessible from the command line.
Parameters
- server
Either a domain name or an IP address expressed in dotted-decimal notation. If this optional field is omitted,
digattempts to use the default name server for your machine.If you specify a domain name,
digresolves the query using the domain name resolver (BIND). If your system does not support DNS, you may have to specify an network address in dotted-decimal notation. Alternatively, if a DNS server is available, that server must be listed in the local hosts database.- domain
The domain name for which you are requesting information. See the
-xoption for a convenient way to specify a reverse translation address query.- query-type
- The type of information (DNS query type) that you are requesting. If you omit this parameter, the default value for query-type is
a(network address). BIND recognizes the following query types:Query Type
Query Class
Description
aT_A
Network address
anyT_ANY
All information about the specified domain
mxT_MX
Mail exchanger for the domain
nsT_NS
Name servers
soaT_SOA
Zone of authority record
hinfoT_HINFO
Host information
axfrT_AXFR
Zone transfer (must ask an authoritative server)
txtT_TXT
Arbitrary number of strings (see RFC 1035 for the complete list)
- query-class
- The network class requested in the query. If you omit this parameter, the default is
in(C_IN, Internet class domain). BIND recognizes the following classes:Query Type
Query Class
Description
inC_IN
Internet class domain
anyC_ANY
All class information
See RFC 1035 for a complete list of query classes.
You can use the
query-class anystatement to specify a class or a type of query.digparses the first occurrence ofanyto meanquery-type = T_ANY. To specifyquery-class = C_ANY, you must either specifyanytwice or setquery-classusing the-coption.
Options
- %ignored-comment
- Use the percent (%) character to include an argument that is not parsed. This can be useful if you are running
digin batch mode. Instead of resolving every@server-domain-namein a list of queries, you can avoid the overhead of doing so, and still have the domain name on the command line as a reference. For example:dig @128.9.0.32 %venera.isi.edu mx isi.edu
- -<dig-option>
- Use the hyphen (-) character to specify an option that affects the operation of
dig. The options described in the Table A.1 are currently available (although not guaranteed to be useful). Options that are uppercase characters must be specified in quotes. For example,dig -"P"Table A.1. dig Options Option
Description
-x dot-notation-addressConvenient form for specifying reverse translation of IP address. Instead of:dig 32.0.9.128.in-addr.arpa
you can use:dig -x 128.9.0.32
-f fileFile for
digbatch mode. The file contains a list of query specifications (digcommand lines) that are to be executed successively. Lines beginning with ;, #, ornare ignored. Other options can still appear on the command line and will be in effect for each batch query.-T timeTime (in seconds) between start of successive queries when running in batch mode. Can be used to keep two or more batch
digcommands running synchronously. The default is 0.-p portPort number. Queries a name server listening to a nonstandard port number. The default is 53.
-PAfter query returns, executes apingcommand to compare response times. This option issues the following command:$ MCR TCPIP$PING "-C" 3 server_nameUse quotation marks to preserve the case of this option.
-t query-typeType of query. Specifies either an integer value to be included in the type field, or uses the abbreviated mnemonic (such as
mx).-c query-classClass of query. Specifies either an integer value to be included in the class field, or use the abbreviated mnemonic (such as
in). - +<query-option>
- Use the plus (+) character to specify an option to be changed in the query packet or to change
digoutput specifics. Many of these options are the same options accepted bynslookup. If an option requires a parameter, use the following format:+ keyword [=value]
Most keywords can be abbreviated. Parsing of the “+” options is very simplistic– a value must not be separated from its keyword by any spaces. The following keywords are currently available:Keyword
Abbreviation
Default
Description
[no] debugdebdebTurn on/off debugging mode.
[
no]d2nod2Turn on or off extra debugging mode.
[
no]recurserecrecUse or do not use recursive lookup.
retry=#ret4Set number of retries to #.
time=#ti4Set timeout length to # seconds.
[
no]konokoKeep open option (implies
vc).[
no]vcnovcUse or do not use virtual circuit.
nodefnamedefdefUse or do not use default domain name.
[
no]searchseaseaUse or do not use domain search list.
domain=NAMEdoSet default domain name to NAME.
[
no]ignoreinoiIgnore or do not ignore truncation errors.
[
no]primaryprnoprUse or do not use primary server.
noaaonlyaanoaaAuthoritative query only flag.
[
no]cmdcmdEcho parsed arguments.
[
no]statsststDisplay query statistics.
[
no]HeaderHHDisplay basic header.
[
no]headerheheDisplay header flags.
[
no]ttlidttttDisplay TTLs.
[
no]clnoclDisplay class information.
[
no]qrnoqrDisplay outgoing query
[
no]replyreprepDisplay reply.
[
no]quesququDisplay question section.
[
no]answerananDisplay answer section.
[
no]authorauauDisplay authoritative section.
[
no]additadadDisplay additional section.
pfdefSet to default display flags.
pfminSet to minimal default display flags.
pfset=#Set display flags to # (# can be hexadecimal, octal, or decimal).
pfand=#Bitwise and display flags with #.
pfor=#Bitwise or display flags with #.
Examples
The following examples show how to use the dig command.
$ dig ; <<>> DiG 8.1 <<>> ;; res options: init recurs defnam dnsrch ;; got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6 ;; flags: qr rd ra; QUERY: 1, ANSWER: 13, AUTHORITY: 0, ADDITIONAL: 13 ;; QUERY SECTION: ;; ., type = NS, class = IN ;; ANSWER SECTION: . 1d20h1m11s IN NS E.ROOT-SERVERS.NET. . 1d20h1m11s IN NS D.ROOT-SERVERS.NET. . 1d20h1m11s IN NS A.ROOT-SERVERS.NET. . 1d20h1m11s IN NS H.ROOT-SERVERS.NET. . 1d20h1m11s IN NS C.ROOT-SERVERS.NET. . 1d20h1m11s IN NS G.ROOT-SERVERS.NET. . 1d20h1m11s IN NS F.ROOT-SERVERS.NET. . 1d20h1m11s IN NS B.ROOT-SERVERS.NET. . 1d20h1m11s IN NS J.ROOT-SERVERS.NET. . 1d20h1m11s IN NS K.ROOT-SERVERS.NET. . 1d20h1m11s IN NS L.ROOT-SERVERS.NET. . 1d20h1m11s IN NS M.ROOT-SERVERS.NET. . 1d20h1m11s IN NS I.ROOT-SERVERS.NET. ;; ADDITIONAL SECTION: E.ROOT-SERVERS.NET. 2d20h1m11s IN A 192.203.230.10 D.ROOT-SERVERS.NET. 2d20h1m11s IN A 128.8.10.90 A.ROOT-SERVERS.NET. 2d20h1m11s IN A 198.41.0.4 H.ROOT-SERVERS.NET. 2d20h1m11s IN A 128.63.2.53 C.ROOT-SERVERS.NET. 2d20h1m11s IN A 192.33.4.12 G.ROOT-SERVERS.NET. 2d20h1m11s IN A 192.112.36.4 F.ROOT-SERVERS.NET. 2d20h1m11s IN A 192.5.5.241 B.ROOT-SERVERS.NET. 2d20h1m11s IN A 128.9.0.107 J.ROOT-SERVERS.NET. 2d20h1m11s IN A 198.41.0.10 K.ROOT-SERVERS.NET. 2d20h1m11s IN A 193.0.14.129 L.ROOT-SERVERS.NET. 2d20h1m11s IN A 198.32.64.12 M.ROOT-SERVERS.NET. 2d20h1m11s IN A 202.12.27.33 I.ROOT-SERVERS.NET. 2d20h1m11s IN A 192.36.148.17 ;; Total query time: 4013 msec ;; FROM: lassie.ucx.lkg.dec.com to SERVER: default -- 16.20.208.53 ;; WHEN: Wed Aug 9 16:42:08 2000 ;; MSG SIZE sent: 17 rcvd: 436
This example shows how to query your default name server for query type NS (default query type) and query class IN (default query class). The output shows the address records for the root name servers and their IP addresses.
$ dig microsoft.com mx ; <<>> DiG 8.1 <<>> microsoft.com mx ;; res options: init recurs defnam dnsrch ;; got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6 ;; flags: qr rd ra; QUERY: 1, ANSWER: 5, AUTHORITY: 12, ADDITIONAL: 8 ;; QUERY SECTION: ;; microsoft.com, type = MX, class = IN ;; ANSWER SECTION: microsoft.com. 2h18m8s IN MX 10 mail2.microsoft.com. microsoft.com. 2h18m8s IN MX 10 mail3.microsoft.com. microsoft.com. 2h18m8s IN MX 10 mail4.microsoft.com. microsoft.com. 2h18m8s IN MX 10 mail5.microsoft.com. microsoft.com. 2h18m8s IN MX 10 mail1.microsoft.com. ;; AUTHORITY SECTION: com. 5d22h12m9s IN NS A.ROOT-SERVERS.NET. com. 5d22h12m9s IN NS E.GTLD-SERVERS.NET. com. 5d22h12m9s IN NS F.GTLD-SERVERS.NET. com. 5d22h12m9s IN NS F.ROOT-SERVERS.NET. com. 5d22h12m9s IN NS J.GTLD-SERVERS.NET. com. 5d22h12m9s IN NS K.GTLD-SERVERS.NET. com. 5d22h12m9s IN NS A.GTLD-SERVERS.NET. com. 5d22h12m9s IN NS M.GTLD-SERVERS.NET. com. 5d22h12m9s IN NS G.GTLD-SERVERS.NET. com. 5d22h12m9s IN NS C.GTLD-SERVERS.NET. com. 5d22h12m9s IN NS I.GTLD-SERVERS.NET. com. 5d22h12m9s IN NS B.GTLD-SERVERS.NET. ;; ADDITIONAL SECTION: mail2.microsoft.com. 2h8m41s IN A 131.107.3.124 mail3.microsoft.com. 2h27s IN A 131.107.3.123 mail4.microsoft.com. 1h53m4s IN A 131.107.3.122 mail5.microsoft.com. 2h8m43s IN A 131.107.3.121 mail1.microsoft.com. 2h8m43s IN A 131.107.3.125 A.ROOT-SERVERS.NET. 2d19h47m37s IN A 198.41.0.4 E.GTLD-SERVERS.NET. 1d9h45m57s IN A 207.200.81.69 F.GTLD-SERVERS.NET. 3h16m16s IN A 198.17.208.67 ;; Total query time: 4019 msec ;; FROM: lassie.ucx.lkg.dec.com to SERVER: default -- 16.20.208.53 ;; WHEN: Wed Aug 9 16:55:42 2000 ;; MSG SIZE sent: 31 rcvd: 493
This example shows how to obtain the mail server records for Microsoft.
ifconfig
ifconfig — Assigns an address to a network interface, and configures and displays network interface parameters.
Syntax
ifconfig interface_id
[address_family]
[address[/bitmask]]
[dest_address]
[parameters])
ifconfig -a [-d] [-u] [-v]
[address_family]
ifconfig -l [-d] [-u] [-v]
[address_family]
ifconfig [-v] interface-id
[address_family]
Description
ifconfig command to define the network address of each
interface. You can also use the ifconfig command at other times to
display all interfaces that are configured on a system, to redefine the address of
an interface, or to set other operating parameters.Note
If you want to redefine the interface address or the net mask, you should stop VSI TCP/IP Services. Otherwise, any TCP/IP process currently running will continue to use the old address and net mask and will fail.
Any user can query the status of a network interface; only a privileged user can modify the configuration of network interfaces.
You specify an interface with the ifconfig
interface-id syntax. (See your hardware
documentation for information on obtaining an interface ID.)
If you specify only interface-id, the ifconfig
program displays the current configuration for the specified network interface
only.
If a protocol family is specified by the address_family
parameter, ifconfig reports only the configuration details specific to
that protocol family.
When changing an interface configuration, if the address family cannot be inferred from the address parameter, an address family must be specified. The address family is required because an interface can receive transmissions in different protocols, each of which can require a separate naming scheme.
The address parameter is the network address of the interface
being configured. For the inet address family, the
address parameter is either a host name or an IP address in
the standard dotted-decimal notation with or without the optional Classless
Inter-Domain Routing (CIDR) bit mask (/bitmask). If you specify
bitmask, do not use the netmask
parameter.
The destination address (dest_address) parameter specifies the address of the correspondent on the remote end of a point-to-point link.
Flags
- -a
Displays information about all interfaces that are configured on a system.
- -d
Displays information about interfaces that are down.
- -l
Displays interface names that are configured on a system.
- -u
Displays information about interfaces that are up.
- -v
Displays detailed information about interfaces, such as hardware addresses.
Parameters
- alias alias_address[/bitmask]
Establishes an additional network address for this interface. This can be useful when changing network numbers and you want to continue to accept packets addressed to the old interface.
If you do not specify a bit mask or net mask with the alias address, the default net mask is based on the alias address's network class.
If you are using the optional bit mask argument, do not use the net mask argument.
- -alias alias_address
Removes the network address specified. This can be used if you incorrectly specified an alias or if an alias is no longer needed. The
-aliasparameter functions in the same manner as the delete parameter.
- aliaslist address_list[/bitmask]
Establishes a range of additional network addresses for this interface. The range can be a comma-separated list or a hyphenated list, and is inclusive. You can also specify the optional CIDR bit mask (/bitmask) argument at the end of the list. Do not use both a comma-separated list and a hyphenated list for a range.
- -aliaslist
Removes a range of network addresses for this interface. This can be useful when deleting network numbers and you want to keep the primary interface address. The
-aliaslistrules are the same as for thealiaslistparameter.
- allmulti
Enables the reception of all multicast packets.
- -allmulti
Disables the reception of all multicast packets.
- arp
Enables the use of the Address Resolution Protocol (ARP) in mapping between network-level addresses and link-level addresses. This parameter is on by default.
- -arp
Disables the use of the ARP. Use of this parameter is not recommended.
- broadcast broad_address
Specifies the address to use to represent broadcasts to the network. The default broadcast address is the address with a host part consisting of all ones (1). Note that the computation of the host part is dependent on
netmask(see the description of the netmask parameter).
- delete [net_address]
Removes the network address specified. Use this parameter if you incorrectly specified an alias or if the alias was no longer needed. If you have incorrectly set an NS address, removing all NS addresses w ill allow you to specify the host portion again.
If no address is specified,
ifconfigdeletes all network addresses for the interface.
- down
Marks an interface as not working (down), which keeps the system from trying to transmit messages through that interface. If possible, the
ifconfigcommand also resets the interface to disable the reception of messages. Routes that use the interface, however, are not automatically disabled.
- [-]fail
Controls the specified interface. You can force the interface to fail by specifying
failand to recover by specifying-fail.
- [-]home
Forces an alias address to be created with a home interface. This option is useful when you are creating an IP address. By default, all primary IP addresses are created with a home interface.
- [-]fs
Creates an IP address that is not managed by failSAFE IP. By default, if the failSAFE IP services is running, all IP addresses are created as failSAFE IP addresses except for those addresses assigned to the loopback interface (LO0) (for example, the localhost address 127.0.0.1.
- ipmtu mtu_value
Alters the size of the maximum transmission unit (MTU) for messages that your system transmits. It might be necessary to reduce the MTU size so that bridges connecting token rings can transfer frames without error.
- metric number
Sets the routing metric, or number of hops, for the interface to the value of number. The default value is zero (0) if number is not specified, indicating that both hosts are on the same network. The routing metric is used by the ROUTED and GATED services, with higher metrics indicating that the route is less favorable.
- netmask mask
Specifies how much of the address to reserve for subdividing networks into sub-networks. This parameter can only be used with an address family of
inet. Do not use this parameter if you are specifying the CIDR mask (/bitmask) with the address parameter, alias parameter, or aliaslist parameter.The
maskvariable includes both the network part of the local address and the subnet part, which is taken from the host field of the address. The mask can be specified as a single hexadecimal number beginning with 0x, in the standard Internet dotted-decimal notation, or beginning with a name.The mask contains ones (1) for the bit positions in the 32-bit address that are reserved for the network and subnet parts, and zeros (0) for the bit positions that specify the host. The mask should contain at least the standard network portion.
The default net mask is based on the address parameter's network class.
- up
Marks an interface as working (up). This parameter is used automatically when setting the first address for an interface, or it can be used to enable an interface after an
ifconfig downcommand. If the interface was reset when previously marked with thedownparameter, the hardware will be reinitialized.
Examples
The following examples show how to use the ifconfig command.
TCPIP> ifconfig sl0 sl0: flags=10
This example shows how to query the status of serial line interface sl0.
TCPIP> ifconfig lo0 inet 127.0.0.1 up
This example shows how to configure the local loopback interface. Only a user with system privileges can modify the configuration of a network interface.
TCPIP> ifconfig ln0 212.232.32.1/22
This example shows how to configure an ln0 interface. The broadcast address is 212.232.35.255 as the 22-bit mask specifies four Class C networks.
TCPIP> ifconfig tra0 130.180.4.1/24 speed 4
This example shows how to configure the token ring interface for a 4 Mb/s token ring with a net mask of 255.255.255.0 in CIDR format.
TCPIP> ifconfig tra0 down TCPIP> ifconfig tra0 speed 16 up
This example shows how to stop the token ring interface and start it for a 16 Mb/s token ring.
TCPIP> ifconfig we0 alias 132.50.40.35/24
This example shows how to add alias 132.50.40.35 with a net mask of 255.255.255.0 in CIDR format to interface we0.
TCPIP> ifconfig we0 aliaslist 132.240.32-36.40-50/24
This example shows how to add network addresses 40 through 50, to subnets 18.240.32, 18.240.33, 18.240.34, 18.240.35, and 18.240.36 with a net mask of 255.255.255.0 in CIDR format to the we0 interface.
TCPIP> ifconfig we0 down delete abort 145.92.16.1: aborting 7 tcp connection(s)
This example shows how to stop Ethernet interface we0, delete all addresses associated with the interface, and close all TCP connections.
TCPIP> ifconfig we0 -alias 145.92.16.2 abort 145.92.16.2: aborting 2 tcp connection(s)
This example shows how to delete the alias address 145.92.16.2 on interface tu0 and close all TCP connections.
TCPIP> ifconfig we0 alias 145.92.16.2 physaddr aa:01:81:43:02:11
This example shows how to associate MAC address aa:01:81:43:02:11 with the alias address 145.92.16.2.
TCPIP> ifconfig we0 -alias 145.92.16.2 -physaddr aa:01:81:43:02:11
This example shows how to disassociate MAC address aa:01:81:43:02:11 from the alias address 145.92.16.2.
A72KT: ifconfig -l TCPIP>ifconfig -l LO0 TN0 WE0
This example shows how to display the names of the interfaces on the system only.
TCPIP> ifconfig -v WE0 wE0: flags=c43<UP,BROADCAST,RUNNING,MULTICAST,SIMPLEX> HWaddr aa:0:4:0:72:f8 inet 10.10.2.2 netmask ffffff00 broadcast 10.10.2.255 ipmtu 1500This example shows how to display the hardware and IP addresses of interface WE0.
ndc
ndc — Manages the BIND server.
Syntax
ndc directive [directive ... ]
Description
This command allows the name server administrator to send various messages to a name server. You can specify zero or more directives from the following list.
Directives
- status
Displays the current status of the BIND server process.
- dumpdb
Causes the BIND server to dump its database and cache to SYS$SPECIFIC:[TCPIP$BIND]TCPIP$BIND_SERVER_ZONES_DUMP.DB.
- reload
Causes the BIND server to check the serial numbers of all primary and secondary zones and to reload those that have changed.
- stats
Causes the BIND server to dump statistics to SYS$SPECIFIC:[TCPIP$BIND]TCPIP$BIND_SERVER_STATISTICS.LOG.
- trace
Causes the BIND server to increment its tracing level by 0. Trace information is written to SYS$SPECIFIC:[TCPIP$BIND]TCPIP$BIND_RUN.LOG. Higher tracing levels result in more detailed information.
- notrace
Causes the BIND server to set its tracing level to 0.
- start
Causes the BIND server to be started, if it is not running.
- stop
Causes the BIND server to be stopped if it is running.
- restart
Causes the BIND server to be stopped and restarted.
Examples
The following examples show how to use the ndc command.
$ ndc status BIND Server process information: Process ID: 44C0021C Process name: TCPIP$BIND_1 Priority: 9 Elapsed CPU time: 0 00:00:31.19 Buffered I/O count: 214082 Direct I/O count: 404 Page Faults: 485 Pages: 4096 Peak virtual size: 173696 Peak working set size: 5920 Process state: LEF
This example shows how to display the current status of the BIND server process.
$ ndc dumpdb
This example shows how to dump the BIND server's database into the SYS$SPECIFIC:[TCPIP$BIND]TCPIP$BIND_SERVER_ZONES_DUMP.DB file. Use the DCL command TYPE to view the contents of this file.
$ ndc stats
This example shows how to dump BIND server statistics to the SYS$SPECIFIC:[TCPIP$BIND]TCPIP$BIND_SERVER_ZONES_STATISTICS.LOG file. Use the DCL command TYPE to view the contents of this file.
netstat
netstat — Displays network-related data in various formats.
Syntax
netstat [-rn] | [-an] [-f address_family]
[interval] ]
netstat [-abd"H"im"M"nrstv] [-f address_family]
[interval]
netstat [-ntdz] ["-I" interface]
[interval]
netstat [-i] [-p protocol]
Description
The interval argument specifies in seconds the interval for updating and displaying information. The first line of the display shows cumulative statistics; subsequent lines show statistics recorded during interval.
Default display
netstat command displays a list of
active sockets for each protocol. The default display shows the following items:Local and remote addresses
Send and receive queue sizes (in bytes)
Protocol
State
Address formats are of the form host.port or
network.port if a socket's address specifies a network but
no specific host address. The host and network address are displayed symbolically
unless -n is specified.
Interface display
Interface name (Name)
Maximum transmission unit (Mtu)
Network address
Packets received (Ipkts)
Packets received in error (Ierrs)
Packets transferred (Opkts)
Outgoing packets in error (Oerrs)
Collisions (Coll)
Note that the collisions item has different meanings for different network interfaces.
Drops (optional with
-d)Timers (optional with
-t)
Routing table display
A route consists of a destination host or network and a gateway to use when
forwarding packets. Direct routes are created automatically for each interface
attached to the local host when you issue the ifconfig command. Routes
can be modified automatically in response to the prevailing condition of the
network.
The routing-table display format indicates available routes and the status of each in the following fields:
Flags
|
U |
Up, or available. |
|
G |
This route is to a gateway. |
|
H |
This route is to a host. |
|
D |
This route was dynamically created by a redirect. |
|
M |
This route was modified by a redirect. |
|
S |
This is a static route that was created by the
|
|
R |
This is a reject route that was created by the
|
refcnt
Gives the current number of active uses for the route. Connection-oriented protocols hold on to a single route for the duration of a connection; connectionless protocols obtain routes in the process of sending to a destination.
use
Provides a count of the number of packets sent using the route.
interface
Indicates the network interface used for the route.
When the -v flag is specified, the routing table display includes
the route metrics. An asterisk (*) indicates the metric is locked.
Flags
- -a
Displays the state of sockets related to the Internet protocol. Includes sockets for processes such as servers that are currently listening at a socket but are otherwise inactive.
- -b
Displays the contents of the Mobile IPv6 binding cache. When used with the -s option, it displays binding cache statistics.
For more information about using netstat with IPv6, refer to the VSI TCP/IP Services for OpenVMS Guide to IPv6.
- -d
Displays the number of dropped packets; for use with the
-Iinterface or-iflags. You can also specify an interval argument (in seconds).- -f address_family
- Limits reports to the specified address family. The address families that can be specified might include the following:
inet
Specifies reports of the AF_INET family, if present in the kernel.
all
Lists information about all address families in the system.
any
Lists information about any address families in the system.
- -H
Displays the current ARP table (behaves like
arp -a.)Use quotation marks to preserve the case of this option.
- -i
Displays the state of configured interfaces. (Interfaces that are statically configured into the system but not located at system startup are not shown.)
When used with the
-aflag,-idisplays IP and link-level addresses associated with the interfaces.You can use the
-iflag to retrieve your system's hardware address.You can use the -p flag to specify a protocol for which to display statistics.
- -I interface
Displays information about the specified interface.
- -p protocol
Displays statistics for the specified protocol. Use the
-iflag with the-pflag.- -m
Displays information about memory allocated to data structures associated with network operations.
- "-M"
Displays Internet protocol multicast routing information. When used with the
-sflag,-Mdisplays IP multicast statistics.- -n
Displays network address in numerical format with network masks in CIDR format. When this flag is not specified, the address is displayed as host name and port number. This flag can be used with any of the display formats.
- -r
Displays the host's routing tables. When used with the
-sflag,-rshows the host's routing statistics instead of its routing tables.- -s
Displays statistics for each protocol.
- -t
Displays timer information. Use with the
-Iinterface or-iflag.- -v
Displays detailed output when specified with the
-rflag. In this case, route metric values are displayed.- -z
Sets the network interface counters to zero. This flag must be specified with the
-Iinterface flag. You must have system privileges to use the-zflag.
Examples
The following examples show how to use the netstat command to display
information about configured interfaces and routing tables.
TCPIP> netstat -i Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll LO0 4096 <Link> Link#1 167 0 167 0 0 LO0 4096 loop LOCALHOST 167 0 167 0 0 SE0 1500 <Link> aa:0:4:0:6d:f8 1544 0 157 0 0 SE0 1500 loop RUFUS 1544 0 157 0 0 TN0* 1280 <Link> Link#2 0 0 0 0 0This example shows how to display the state of the configured interfaces.
TCPIP> netstat -r Routing tables Destination Gateway Flags Refs Use Interface Route Tree for Protocol Family 26: Route Tree for Protocol Family 2: default sqagate UG 0 0 SE0 10.10.2 v72kt U 2 125 SE0 v72kt v72kt UHL 0 50 SE0 LOCALHOST LOCALHOST UHL 7 117 LO0This example shows how to display the routing tables.
TCPIP> netstat -rn Routing tables Destination Gateway Flags Refs Use Interface Route Tree for Protocol Family 26: Route Tree for Protocol Family 2: default 10.10.2.66 UG 0 0 SE0 10.10.2/24 10.10.2.4 U 2 109 SE0 10.10.2.4 10.10.2.4 UHL 0 50 SE0 127.0.0.1 127.0.0.1 UHL 7 117 LO0This example shows how to display the routing tables with network addresses.
nslookup
nslookup — Queries Internet name servers interactively.
Syntax
nslookup [-option ...]
[host_to_find | - [server]
]
Description
nslookup command is a program that is used to query Internet
domain name servers. The nslookup command has two modes: noninteractive
and interactive.Note
The nslookup utility is deprecated. VSI recommends that you
use the dig utility instead. For information about the dig
utility, see the VSI TCP/IP Services for OpenVMS Management guide.
Noninteractive mode
Noninteractive mode is used to display just the name and requested information for a host or domain. Noninteractive mode is invoked when the name or Internet address of the host to be looked up is given as the first argument. The optional second argument specifies the host name or address of a name server.
Interactive mode
Interactive mode allows the user to query name servers for information about
various hosts and domains or to display a list of hosts in a domain. Interactive
mode is invoked when you specify nslookup without arguments (the
default name server will be used), or when the first argument you specify is a
hyphen (-) and the second argument is the host name or IP address of a name
server.
set command can be specified in the
.nslookuprc file in the user's home directory if they are listed
one per line. Options can also be specified on the command line if they precede the
arguments and are prefixed with a hyphen (-). For example, to change the default
query type to host information, and the initial time out to 10 seconds, enter the
following
command:$ nslookup -query=hinfo -timeout=10
Interactive commands
Commands can be interrupted at any time by pressing Ctrl/C. To exit, press Ctrl/D
(EOF) or type exit. The command line length must be less than 256
characters. To treat a built-in command as a host name, prefix it with an escape
character (^) plus a backslash (\). Note that an unrecognized command will be
interpreted as a host name.
Commands
- host [server]
Looks up information for the host using either the current default server or the specified server. If
hostis an IP address and the query type is A or PTR, the name of the host is returned. Ifhostis a name and does not have a trailing period, the default domain name is appended to the name. (This behavior depends on the state of thesetoptionsdomain,srchlist,defname, andsearch.) To look up a host not in the current domain, append a dot (.) to the end of the domain name.- server domainlserver domain
Changes the default server to
domain. Thelservercommand uses the initial server to look up information aboutdomain, while theservercommand uses the current default server. If an authoritative answer cannot be found, the names of servers that might have the answer are returned.- root
Changes the default server to the server for the root of the domain name space. Currently, the host
ns.internic.netis used. (This command is a synonym forlserver ns.internic.net.) The name of the root server can be changed with theset rootcommand.- finger [name] [> filename]finger [name] [>> filename]
Connects with the
fingerserver on the current host. The current host is defined when a previous lookup for a host was successful and returned address information (see theset querytype=Acommand). The redirection symbols (> and >>) can be used to redirect output in the usual manner.- ls [option] domain [> filename]ls [option] domain [>> filename]
- Lists the information available for domain, optionally creating or appending to filename. The default output contains host names and their IP addresses. The value for
optioncan be one of the following:Option
Description
-tquerytypeLists all records of the specified type. (See
querytypein Table A.2.)-aLists aliases of hosts in the domain. This option is a synonym for
-t CNAME.-dLists all records for the domain. This option is a synonym for
-t ANY.-hLists CPU and operating system information for the domain. This option is a synonym for
-t HINFO.-sLists well-known services of hosts in the domain. This option is a synonym for
-t WKS. When output is directed to a file, a pound sign (#) is displayed for every 50 records received from the server. - view filename
Sorts and lists the output of previous
lscommands.- help
Displays a brief summary of commands.
- exit
Exits the program.
- set keyword [=value]
- Use the command to change state information that affects the lookups. Table A.2 lists the valid keywords.
Table A.2. Options to the nslookup setCommandKeyword Function
ALLDisplays the current values of the options you can set as well as information about the current default server. For example:> set all
class=valueChanges the query class to one of the following:The class specifies the protocol group of the information. You abbreviate this keyword toIN— The internet class (default)CHAOS— The chaos classANY— Wildcard
cl. This command tellsnslookupto resolve bothinandchaosclass queries (you can enterinandchaos):> set class=ANY
querytypeSpecifies the type of information you want. For example:> set querytype=A > set querytype=ANY
Valid types are:
SOA
Start of authority. Marks the beginning of a zone's data and defines parameters that affect the entire zone.
NS
Name server. Identifies a domain's name server.
A
Address. Maps a host name to an address.
ANY
Defines all available resource records for a given name.
PTR
Pointer. Maps an address to a host name.
MX
Identifies where to deliver mail for a given domain.
CNAME
Defines an alias host name.
HINFO
Host information. Describes a host's hardware and operating system.
WKS
Well-known service. Advertises network services.
[no]debugTurns on debugging (default isnodebug).nslookupdisplays detailed information about the packet sent to the server and the answer. For example:> set debug
You can use the abbreviations
nodebanddeb.[no]d2Returns all-inclusive debugging information (default isnod2). Displays all the fields of every packet. For example:> set d2
recurseTells the BIND server to contact other servers if it does not have the information you want. The servers carry out a complete (recursive) resolution for each query. For example:> set recurse
retryNumber of times thatnslookupattempts to contact a BIND server if repeated tries fail. For example:> set retry=8
timeoutLength of time to wait for a reply from each attempt. For example:> set timeout=9
root=valueChanges the root server. For example, the following command changes the root server tons.nasa.gov.> set root=ns.nasa.gov
ignoretcTellsnslookupto ignore packet truncation errors. For example:> set ignoretc
domain nameChanges the default domain to the domain you specify. The settings of the
defnameandsearchoptions control how the default domain name is appended to lookup requests. The domain search list contains the parents of the default domain if the default domain has at least two components in its name. The default value is set in the TCP/IP configuration database. To specify the default, type the abbreviationdo. For example, if the default domain isCC.Berkeley.EDU, the search list isCC.Berkeley.EDUandBerkeley.EDU.srchlistIf set,
nslookupappends each of the domain names specified in thesrchlistoption to an unqualified host name and performs a query until an answer is received.srchlist=namesChanges the default domain name to the first name you specify, and changes the domain search list to all the names you specify. Specify a maximum of six names separated by slashes (/). In the following example, the command sets the default domain tolcs.MIT.EDUand changes the search list to the three specified domains. The command overrides the default domain name and associated search list for theset domaincommand.> set srchlist=lcs.MIT.EDU/ai.MIT.EDU/MIT.EDU
The default is the domain name specified in the TCP/IP configuration database. The abbreviated form of the command issrchl.[no]defnameTells
nslookupto append a default domain name to a lookup request if the specified DNS name is not fully qualified.?The abbreviated form is[no]def. For example, annslookupquery for the hostrainybecomesrainy.cc.berkeley.edu.[no]searchTells
nslookupto append the search list domain names to the lookup request domain name if the lookup request domain name is not fully qualified.?The default issearch. The abbreviated form is[no]sea.
Examples
The following example shows how to use nslookup interactively.
$ nslookup Default Server: condor.lgk.dec.com Address: 16.99.208.53 > set all Default Server: condor.lgk.dec.com Address: 16.99.208.53 Set options: nodebug defname search recurse nod2 novc noignoretc port=53 querytype=A class=IN timeout=4 retry=4 root=a.root-servers.net. domain=xyz.prq.dec.com srchlist=xyz.prq.dec.com
ping
ping — Send ICMP ECHO_REQUEST packets to network hosts.
Syntax
ping [-dfnqruvR] -c count [-i
wait] [-l preload] [-p
pattern] [-s packetsize]
host
Description
The ping command uses the ICMP (Internet Control Message Protocol)
mandatory ECHO_REQUEST datagram to elicit an ICMP ECHO_RESPONSE message from the
specified host or gateway host. ECHO_REQUEST datagrams (ping) have an
IP (Internet Protocol) and ICMP header, followed by a struct timeval
and then an arbitrary number of pad bytes used to fill out the packet.
When using ping for fault isolation, first run the command on the
local host to verify that the local network interface is up and running. Then, hosts
and gateways further and further away should be sent the ping command.
Round-trip times and packet loss statistics are computed. If duplicate packets are
received, they are not included in the packet loss calculations, although the
round-trip time of these packets is used in calculating the minimum, average, and
maximum round-trip time numbers. When the specified number of packets have been sent
(and received), or if the program is terminated with a SIGINT, a brief summary is
displayed.
This program is intended for use in network testing, measurement, and management.
Because of the load it can impose on the network, it is unwise to use
ping during normal operations or from automated scripts.
ICMP packet details
An IP header without options is 20 bytes. An ICMP ECHO_REQUEST packet contains an additional 8 bytes worth of ICMP header followed by an arbitrary amount of data. When a packetsize is given, this indicates the size of this extra piece of data (the default is 56). Thus, the amount of data received inside of an IP packet of type ICMP ECHO_REPLY will always be 8 bytes more than the requested data space (the ICMP header).
If the data space is at least 8 bytes large, ping uses the first 8
bytes of this space to include a timestamp, which it uses in the computation of
round-trip times. If less than 8 bytes of pad are specified, no round-trip times are
given.
Duplicate and damaged packets
The ping command will report duplicate and damaged packets. Duplicate
packets should never occur, and seem to be caused by inappropriate link-level
retransmissions. Duplicates can occur in many situations and are rarely (if ever) a
good sign, although the presence of low levels of duplicates can not always be cause
for alarm.
Damaged packets are obviously serious cause for alarm and often indicate broken
hardware somewhere in the ping packet's path (in the network or in the
hosts).
Different data patterns
The network layer should never treat packets differently depending on the data contained in the data portion. Unfortunately, data-dependent problems have been known to invade networks and remain undetected for long periods of time. In many cases the problematic pattern does not have sufficient transitions, such as all ones (1) or all zeros (0), or has a pattern at the right, such as almost all zeros (0). It is not necessarily enough to specify a data pattern of all zeros on the command line because the problematic pattern of interest is at the data-link level, and the relationship between what you enter and what the controllers transmit can be complicated.
Data-dependent problems can be identified only by extensive testing. If you are
lucky, you can manage to find a file that either cannot be sent across your network
or that takes much longer to transfer than other files of similar length. You can
then examine this file for repeated patterns that you can test by using the
-p option to the ping command.
TTL details
The TTL value of an IP packet represents the maximum number of IP routers that the packet can go through before being thrown away. You can expect each router in the Internet to decrement the TTL field by exactly one.
The maximum possible value of this field is 255, and most UNIX compatible systems
set the TTL field of ICMP ECHO_REQUEST packets to 255. This is why you can use the
ping command on some hosts but not reach them with
TELNET or FTP.
ping displays the TTL value from the packet it
receives. When a remote system receives a ping packet, it can do one of
three things with the TTL field in response:Not change the field. This is what Berkeley UNIX compatible systems did before BSD Version 4.3. In this case, the TTL value in the received packet will be 255 minus the number of routers in the round-trip path.
Set the field to 255. This is what current Berkeley UNIX compatible systems do. In this case, the TTL value in the received packet will be 255 minus the number of routers in the path from the remote system to the host that received the
pingcommands.Set the field to some other value. Some machines use the same value for ICMP packets that they use for TCP packets; for example, either 30 or 60. Others may use completely wild values.
Cautions
Many hosts and gateways ignore the RECORD_ROUTE option.
Flooding and preloading the ping command is generally not
recommended, and flooding ping messages on the broadcast address should
be done only under very controlled conditions.
Flags
- -c count
Stops after sending (and receiving) the specified number (count) of ECHO_RESPONSE packets.
- -d
Sets the
SO_DEBUGoption on the socket being used.- -f
Floods
ping. Outputs packets as fast as they come back or 100 times per second, whichever is more. For everyECHO_REQUESTsent, a dot (.) is displayed, while for everyECHO_REPLYreceived a backspace is used. This provides a rapid display of how many packets are being dropped. You must have system privileges to use this option. Using the-fflag can be very hard on a network and should be used with caution.- -i wait
Waits the specified number of seconds between sending each packet. The default is to wait for 1 second between each packet. This option is incompatible with the
-foption.- -l preload
If preload is specified,
pingsends that many packets as fast as possible before falling into its normal mode of behavior. You must have system privileges to use this option. Using the-loption can be very hard on a network and should be used with caution.- -n
Numeric output only. No attempt is made to look up symbolic names for host addresses. This occurs only when displaying ICMP packets other than ECHO_RESPONSE.
- -p pattern
Specifies up to 16 pad bytes to fill out the packet you send. This is useful for diagnosing data-dependent problems in a network. For example,
-p ffwill cause the sent packet to be filled with all ones (1).- -q
Suppresses output. Nothing is displayed except the summary lines at startup time and at completion.
- -R
Records route. Includes the RECORD_ROUTE option in the ECHO_REQUEST packet and displays the route buffer on returned packets. Note that the IP header is large enough for only nine such routes. Many hosts ignore or discard this option.
- -r
Bypasses the normal routing tables and sends directly to a host on an attached network. If the host is not on a directly attached network, an error is returned. This option can be used to send
pingto a local host through an interface that has no route through it (for example, after the interface was dropped by ROUTED).- -s packetsize
Specifies the number of data bytes to be sent. The default is 56, which translates into 64 ICMP data bytes when combined with the 8 bytes of ICMP header data.
- -u
Displays the time in microseconds (three decimal places). In order to ensure this microsecond precision, the NTP_TIME and MICRO_TIME kernel options must be on. By default, NTP_TIME and MICRO_TIME kernel options are off. If these kernel options are off and this flag is used, the time is displayed to three decimal places, but in milliseconds.
- -v
Specifies detailed output. ICMP packets other than ECHO_RESPONSE that are received are listed.
Examples
ping command.TCPIP> ping PING rufus.lkg.dec.com (10.10.2.4): 56 data bytes 64 bytes from 10.10.2.4: icmp_seq=0 ttl=64 time=30 ms 64 bytes from 10.10.2.4: icmp_seq=1 ttl=64 time=0 ms 64 bytes from 10.10.2.4: icmp_seq=2 ttl=64 time=0 ms 64 bytes from 10.10.2.4: icmp_seq=3 ttl=64 time=0 ms ----rufus.lkg.dec.com PING Statistics---- 4 packets transmitted, 4 packets received, 0% packet loss round-trip (ms) min/avg/max = 0/8/30 ms
route
route — Manually manipulates the routing tables.
Syntax
route [-nqvC] add [-net | -host] [family] destination[/bitmask] gateway
[-link] [modifiers [args]]
route [-nqv] change [-net | -host] [family] destination gateway
[-link] [modifiers
args]
route [-n] monitor
route [-nqvC] delete [-net | -host] [family] destination[/bitmask] [-link]
gateway [modifiers
args]
route [-nqvC] flush [family]
Description
The route command allows you to manually manipulate the network
routing tables. It normally is not needed, since a system-routing table management
daemon, such as GATED or ROUTED, should tend to this task.
route command accepts five commands:|
|
Adds a route. |
|
|
Removes all routes. |
|
|
Deletes a specific route. |
|
|
Changes aspects of a route (such as its gateway). |
|
|
Reports any changes to the routing information base, r' lookup misses, or suspected network partitions. |
flush command has the following
format:route [-n] flush [family]In this format, the address family can be specified by the -inet
keyword.
route [-n] command [-net | -host] destination[/bitmask] gateway modifier [-netmask mask]
Unless the net or the host parameter is specified on the command line, route creates a host route or a network route by interpreting the Internet address associated with destination parameter. If the destination has a local address part of INADDR_ANY, or if the destination is the symbolic name of a network, a network route is created; otherwise, a host route is created.
For example, 128.32 is interpreted as -host 128.0.0.32,
128.32.130 is interpreted as -host 128.32.0.130; -net
128.32 is interpreted as 128.32.0.0, and -net
128.32.130 is interpreted as 128.32.130.0.
All symbolic names specified for a destination or gateway are looked up first as a
host name using gethostbyname(). If this lookup fails,
getnetbyname() is then used to interpret the name as that of a
network.
Routes added with the route command are marked as RTF_STATIC to differentiate them from routes added by the routing daemons (GATED or ROUTED). The GATED daemon does not remove the RTF_STATIC routes when it is shut down.
The route utility uses a routing socket and the new message types
RTM_ADD, RTM_DELETE, and RTM_CHANGE. As such, only a privileged user can modify the
routing tables.
Flags
- -n
Prevents attempts to display host and network names symbolically when reporting actions.
- -v
Displays additional details.
- -q
Suppresses all output.
Modifiers
- -all
Specifies that the kernel add or delete the specified route on all interfaces (for example,
TU0andTU1) that are in the same subnet as the gateway. Use this modifier only with theaddanddeletemodifiers. Do not use-allwith the-devand-olddevmodifiers.- -blackhole
Specifies that this route is a blackhole route. Packets sent to blackhole routes are dropped, and notification is not sent to the packet originators. This is different from a normal route, which allows packets to be forwarded out on it. You must specify
127.0.0.1(localhost) as the gateway argument.- -cloning
Generates a new route on use of this route.
- -dev device
Specifies the interface device to use in the routing entry. Use this modifier when you want to designate a particular interface for a route. If you do not specify this modifier, the route is added on the first interface that is found.
- -genmask mask
Specifies that the netmask mask is used for all routes cloned from this route.
- -hopcount count
Sets this route's maximum hopcount to the value specified by count.
- -iface | -interface
Specifies that this route is through an interface instead of through a gateway (gateway is the default). This means the destination is reachable directly through an interface; no intermediate system is required. The gateway parameter is the host address to be used for transmission.
- -inet
Sets this route's type as AF_INET. When you specify
inetwith thedeleteorflushcommand, only AF_INET routes are deleted.- -llinfo
Specifies that this route contains valid link-layer information.
- -lock
Locks the metric specified by the next modifier specified on the command line. A locked metric is not modified by the kernel. The following metrics can be locked:
mtu,hopcount,recvpipe,sendpipe,ssthresh,rtt, andrttvar.- -lockrest
Locks the metrics specified by all the modifiers that follow on the command line. A locked metric is not modified by the kernel. The following metrics can be locked:
mtu,hopcount,recvpipe,sendpipe,ssthresh,rtt, andrttvar.- -mtu size
Sets this route's maximum transmission unit (MTU) (in bytes) to the value specified by size.
- -netmask mask
Specifies the subnet mask to use for the routing entry. Networks that use a nonstandard subnet must include this modifier. Specify this modifier after any optional modifiers. Do not specify this modifier if you specify a CIDR bitmask (/bitmask). Do not specify this modifier with the
changecommand.- -nofragtopmtu
Specifies that IP datagram fragmentation is disabled for this route.
- -nopmtudisc
Specifies that path MTU discovery is disabled for this route.
- -olddev device
Specifies the old interface device that you want to change in the routing entry. Use this modifier with the
changecommand only to move a route from one interface to another.- -oldgateway name
Specifies the old gateway that you want to change in the routing entry. Use this modifier with the
changecommand only.- -precedence value
Sets the precedence of the route to the value specified by value. Among equivalent routes to the same destination, the route with the lower precedence is preferred.
- -recvpipe bandwidth
Sets this route's inbound delay bandwidth product (in bytes) to the value specified by bandwidth.
- -reject
Specifies that this route is a reject route. Packets sent to reject routes are dropped, and messages designating the route as unreachable are sent to the packet originators. This is different from a normal route, which allows packets to be forwarded out on it. You must specify
127.0.0.1(localhost) as the gateway argument.- -rtt time
Sets this route's round-trip time (in microseconds) to the value specified by time.
- -rttvar variance
Sets this route's round-trip time variance (in microseconds) to the value specified by variance.
- -sendpipe bandwidth
Sets this route's outbound delay bandwidth product (in bytes) to the value specified by bandwidth.
- -ssthresh threshold
Sets this route's outbound gateway buffer limit (in bytes) to the value specified by threshold.
Examples
route utility.TCPIP> route add default 128.32.0.130
The example shows how to add gateway 128.32.0.130 as a default gateway.
TCPIP> route add -host milan 128.32.0.130
The example shows how to add a route to host
milanvia gateway128.32.0.130.TCPIP> route delete -host milan 128.32.0.130
The example shows how to delete an existing route via gateway
128.32.0.130to hostmilan.TCPIP> route add -precedence 1 -host milan 128.32.0.130
The example shows how to add a route with a precedence value of 1 to host
milanvia gateway128.32.0.130.TCPIP> route change -oldgateway 128.32.0.130 -oldinterface le0 - _TCPIP> -host milan 128.32.10.101
The example shows how to change an existing route for host
milanvia gateway128.32.0.130to use a new gateway128.32.10.101.
sysconfig
sysconfig — Maintains the kernel subsystem configuration.
Syntax
sysconfig - -c | -d | -m | -q | "-Q" | -r | -s | -u
[subsystem-name] [attribute-list]
Description
The sysconfig command queries and modifies the in-memory subsystem
configuration. Use this command to add subsystems, reconfigure subsystems that are
already in memory, query subsystems, and unconfigure and remove subsystems.
The sysconfig utility allows you to modify the value of subsystem
attributes, as long as the subsystem supports run-time modifications.
When you configure a subsystem using the -c flag, you make that
subsystem available for use. If the subsystem is loadable, the
sysconfig command loads the subsystem and then initializes the
value of its attributes.
To modify the value of a subsystem attribute, use the -r
(reconfigure) flag. Specify the subsystem attributes and values on the command line.
The sysconfig utility modifies the named attributes by storing the
value you specify in them. The modifications take effect immediately.
To get information about subsystem attributes, use either the -q flag
or the "-Q" flag. You can specify an attribute list with both these
flags. When you use the -q flag, the sysconfig command
displays the value of attributes from the in-memory system configuration
table.
When you use the "-Q" flag, the sysconfig utility
displays the following information about each attribute you specify in the attribute
list or, if you omit the attribute list, every attribute for the specified
subsystem. You must enclose the "-Q" flag in quotation marks to
preserve its case.
Attribute datatype.
- Operations supported by the attribute. The op code indicates whether the attribute can be:
Configured
Reconfigured
Queried
For example, if
op=RCQ, the attribute can be configured (using thesysconfigdbutility), reconfigured (using thesysconfig -rcommand), and queried (using thesysconfig -qcommand). Minimum and maximum allowed attribute values.
To get information about the state of subsystems, use the -s flag.
This flag provides a list of the subsystems that are currently loaded and
configured. If you specify subsystem-name, the
command displays information about the state of that subsystem. Each subsystem can
have one of three states:
Loaded and configured (available for use)
Loaded and unconfigured (not available for use but still loaded)
This state applies only to static subsystems, which can be unconfigured but cannot be unloaded.
Unloaded (not available for use)
This state applies only to loadable subsystems, which are automatically unloaded when you unconfigure them with the
sysconfig -ucommand.
Subsystems that are not being used can be unconfigured using the -u
flag. Unconfiguring subsystems can free up kernel memory, making it available for
other uses. You can unconfigure any static or loadable subsystem that supports
run-time unconfiguration. If you unconfigure a loadable subsystem, that subsystem is
also unloaded from the kernel.
You can use the sysconfig command to display the value of attributes
on the local system. If you want to configure, reconfigure, or unconfigure a
subsystem, you must be authorized to modify the kernel configuration. Only users who
have a system group UIC or who have an account with SYSPRV, BYPASS, or OPER
privilege can configure, reconfigure, or unconfigure the subsystems.
Parameters
- subsystem-name
Specifies the subsystem on which you want to perform the operation. The subsystem-name argument is required for all flags except
-sand-m. If you omit subsystem-name when you use the-sor-mflag, the sysconfig utility displays information about all loaded subsystems.- attribute-list
Specifies attribute names and, depending on the operation, attribute values.
- For reconfigure (
-r) operations, the attribute-list argument has the following format:attribute1=value1 attribute2=value2...
Do not include spaces between the attribute name, the equals sign (=), and the value.
- For query attribute (
-q) operations, the attribute-list argument has the following format:attribute1 attribute2...
The attribute-list argument is required when
you use the -r flag and is optional with the -q flag. Any
attribute list specified with other flags is ignored by the sysconfig
utility.
Flags
- -c
Configures the specified subsystem by initializing its attribute values and, possibly, loading it into memory. Use this command whether you are configuring a newly installed subsystem or one that was removed using the
sysconfig -ucommand option.- -d
Displays the attribute settings in the SYSCONFIGTAB.DAT file for the specified subsystem.
- -m
Queries the mode for the specified subsystems. A subsystem's mode can be static or dynamic. If you omit the subsystem name,
sysconfigdisplays the mode of all the configured subsystems.- -q
Queries attribute values for the configured subsystem specified by subsystem-name. If you omit the attribute list, values for all the specified subsystem's attributes are displayed.
- "-Q"
Queries information about attributes of the configured subsystem specified by
subsystem-name. The information includes the attribute data type, the operations supported, and the minimum and maximum values allowed for the attribute. Note that the minimum and maximum values refer to length and size for attributes ofcharandbinarytypes, respectively. If you omit theattribute-listargument, information about all attributes in the specified subsystem is displayed.- -r
Reconfigures the specified subsystem. You must supply the subsystem name and the attribute list when you use this flag.
- -s
Queries the subsystem state for the specified subsystems. If you omit the subsystem name,
sysconfigdisplays the state of all the configured subsystems.- -u
Unconfigures and, if the subsystem is loadable, unloads the specified subsystem from the kernel.
Examples
The following examples show how to use the sysconfig command.
TCPIP> sysconfig -s inet: loaded and configured net: loaded and configured socket: loaded and configured iptunnel: loaded and configured ipv6: loaded and configured snmpinfo: loaded and configured
This example shows how to display the subsystems and their status.
TCPIP> sysconfig -q net net: ifnet_debug = 0 ifqmaxlen = 1024 lo_devs = 1 lo_def_ip_mtu = 4096 nslip = 0
This example shows how to display subsystem attributes and their values.
TCPIP> sysconfig -s net net: loaded and configured
This example shows how to query the state of a particular subsystem.
sysconfigdb
sysconfigdb — Manages the subsystem configuration database.
Syntax
sysconfigdb {-a | -u} [-t target] -f
file
subsystem-name
sysconfigdb {-m | -r} [-t target] -f
file [subsystem-name]
sysconfigdb -d [-t target] subsystem-name
sysconfigdb -l [-t target] [subsystem-name,...]
Description
The sysconfigdb utility is used to manage the subsystem configuration
table (TCPIP$ETC:SYSCONFIGTAB.DAT). To specify another file as a target
file, use the -t flag.
To modify a target file, create a stanza file. This stanza file contains the name of one or more subsystems, each with a list of attributes and their values, as described in Section 2.1.3.1.
Modifications that you make to the sysconfigtab are changed the next
time the subsystem is reloaded.
When the target file is another file, there is no synchronization with the subsystem configuration database.
Restrictions
You must have system management privileges to run the sysconfigdb utility to modify the system configuration table.
Parameters
- subsystem-name
Specifies a subsystem that contains the attributes you want to modify. The subsystem name and attributes are in a stanza input file.
You must specify the subsystem name when deleting (
-d), adding (-a), or replacing (-u) a subsystem.In other cases, when you do not specify a subsystem name, the operation is attempted for all the subsystems and attributes specified in the input file.
Flags
- -a
Adds the specified subsystem entry to the target file.
- -d
Deletes the specified subsystem entry from the target file.
- -f file
Specifies the input file, a stanza file that contains entries for one or more subsystems. The default target file is the SYSCONFIGTAB.DAT file. Specify another target file by using the
-ttarget flag.- -l
Lists the specified subsystem entries in the target file. If you do not specify a subsystem name, all subsystem entries in the target file are listed. The SYSCONFIGTAB.DAT file is the default target file.
- -m
Merges subsystem attributes specified in the input file with the subsystem attributes in the target file. If you do not specify a subsystem name, all subsystem entries in the input file are merged. The SYSCONFIGTAB.DAT file is the default target file.
- -r
Removes the subsystem entries specified in the input file from the target file. The only entries removed are those that have attribute names and values that exactly match those in the input file. If you do not specify the subsystem name, all subsystem entries in the input file with attributes that match are removed from the target file. The SYSCONFIGTAB.DAT file is the default target database file.
- -t file
Specifies the target file for the operation. If you do not specify this flag, the default target file is the SYSCONFIGTAB.DAT file.
- -u
Replaces a subsystem entry in the target file with the subsystem entry specified in the input file.
Examples
The following examples show how use the sysconfigdb utility.
$ TCPIP TCPIP> sysconfigdb -u -f table_mgr.stanza table_mgr_1
This command replaces thetable_mgr_1entry in the SYSCONFIGTAB.DAT file with the information in the TABLE_MGR.STANZA file for thetable_mgr_1subsystem. The command updates the in-memory copy of the subsystem configuration database to match the modified SYSCONFIGTAB.DAT file.TCPIP> sysconfigdb -m -f table_mgr.stanza tbl_mgr_2
This command merges thetbl_mgr_2information from thetable_mgr.stanzafile with the information already in thetbl_mgr_2entry in the SYSCONFIGTAB.DAT file. The command updates the in-memory copy of the subsystem configuration database to match the modified SYSCONFIGTAB.DAT file.TCPIP> sysconfigdb -l table_mgr_1 table_mgr_1: size = 10 name = Ten-Element-TableThis command lists the entry for the subsystemtable_mgr_1. This command does not update the in-memory copy of the subsystem configuration database.TCPIP> sysconfigdb -d table_mgr_1
This command deletes thetable_mgr_1entry from the SYSCONFIGTAB.DAT file and updates the in-memory copy of the subsystem configuration database to match the modified SYSCONFIGTAB.DAT file.
tcpdump
tcpdump — Provides dump analysis and packet capturing.
Syntax
tcpdump ["-B" | d | e | f | l | m | n | "-N" | "-O" | q | s | "-S" | t |
v | x | "-X"]
[-b buffers]
[-c count]
[-F file]
[-r file]
[-s snaplen]
[-w file] expression
Description
The tcpdump utility displays the headers and contents of packets on
the network that match a boolean expression (filter). If no filter is supplied all
packets processed by tcpdump will be displayed. The the packets that
are processed can also be written to a binary file for later examination and
filtering.
Parameters
- expression
A boolean expression that provides a filter to select the packets to dump. If you do not specify the expression, all packets on the network are dumped. Otherwise, only packets that match the expression are dumped.
For information about specifying expressions, refer to Section 1.2.5.2.
Options
- -b
Specifies the number of buffers used to communicate with the TCP/IP kernel. The default is 400 on Alpha systems and 50 on VAX systems.
- "-B"
Displays buffer diagnostics showing when dropped packets occur. Use quotation marks to preserve the case of uppercase options.
- -c
Exits after receiving count packets.
- -d
Dumps the compiled packet-matching code to standard output and stops.
- -e
Displays the link-level header on each dump line.
- -f
Displays foreign internet addresses numerically rather than symbolically.
- "-F" file
Uses file as input for the filter expression. Any additional expressions on the command line are ignored. Use quotation marks to preserve the case of uppercase options.
- -l
Buffers the
stdoutline. This is useful if you want to see the data while capturing it.- -m
Enables multiline output from some protocols. This affects most ONC RPC decoding, as those protocols are often difficult to display on a single line.
- -n
Does not convert addresses (for example, host addresses and port numbers) to names.
- "-N"
Does not display domain name qualification of host names. For example, with this option,
tcpdumpdisplaysnicinstead ofnic.ddn.mil. Use quotation marks to preserve the case of uppercase options.- "-O"
Does not run the packet-matching code optimizer. This is useful only if you suspect a bug in the optimizer. Use quotation marks to preserve the case of uppercase options.
- -q
Quick (quiet) output. Displays less protocol information so output line are shorter.
- -r file
Reads packets from file (which was created with the
-woption). Standard input is used if a hyphen (-) is used to specify the file.- -s snaplen
Displays the number of bytes of data from each packet as specified by the value of snaplen, rather than the default of 68. The default of 68 bytes is adequate for IP, ICMP, TCP, and UDP, but may truncate protocol information from name server and NFS packets. Packets truncated because of a limited snapshot are indicated in the output with
[|proto], where proto is the name of the protocol level at which the truncation has occurred.Note
Taking larger snapshots both increases the amount of time it takes to process packets and decreases the amount of packet buffering. This may cause packets to be lost. You should limit the value of
snaplento the smallest number that will capture the protocol information you need.- "-S"
Displays absolute, rather than relative, TCP sequence numbers. Use quotation marks to preserve the case of uppercase options.
- -t
Does not display a timestamp on each dump line.
- -tt
Displays an unformatted timestamp on each dump line.
- -v
Displays verbose output. For example, the time to live and type of service information in an IP packet is displayed. If
-mis also specified, ONC RPC packets sent using TCP are decoded twice: first as RPC, then as TCP. By default, the TCP decoding is suppressed.- -vv
Displays detailed verbose output. For example, additional fields are displayed from NFS reply packets.
- -w file
Writes the raw packets to file rather than parsing and displaying them. They can later be displayed with the
-roption. Standard output is used if a hyphen (-) is used to specify the file.- -x
Displays each packet (minus its link level header) in hexadecimal format.
The smaller of the entire packet or snaplen bytes is displayed.
- "-X"
Displays packets in both hexadecimal and ASCII formats. Use quotation marks to preserve the case of uppercase options.
Examples
$ tcpdump host sundown
This example shows how to use the tcpdump utility to display all packets arriving at or departing from hostsundown.$ tcpdump host sundown and ( hot or ace )
This example shows how to use the tcpdump utility to display traffic between sundown and either host hot or host ace.$ tcpdump ip host ace and not helios
This example shows how to use the tcpdump utility to display all IP packets between ace and any host excepthelios.$ tcpdump net office
This example shows how to use the tcpdump utility to display all traffic between local hosts and hosts on the networkoffice.$ tcpdump gateway snup and (port 21 or 20)
This example shows how to use the tcpdump utility to display all FTP traffic through Internet gatewaysnup.$ tcpdump ip and not net localnet
This example shows how to use the tcpdump utility to display traffic neither sourced from nor destined for local hosts. If your network is connected to one other network by a gateway, this command does not produce any results on your local network.$ tcpdump tcp[13] & 3 != 0 and not src and dst net localnet
This example shows how to use the tcpdump utility to display the start and end packets (the SYN and FIN packets) of each TCP conversation that involves a nonlocal host.$ tcpdump gateway snup and ip[2:2] > 576
This example shows how to use the tcpdump utility to display IP packets longer than 576 bytes sent through gateway snup.$ tcpdump ether[0] & 1 = 0 and ip[16] >= 224
This example shows how to use the tcpdump utility to display IP broadcast or multicast packets that were not sent using Ethernet broadcast or multicast.$ tcpdump icmp[0] != 8 and icmp[0] != 0
This example shows how to use the tcpdump utility to display all ICMP packets that are not echo requests or replies (that is, not PING packets).$ tcpdump -s 1500 -envv ipv6 and udp port 521
This example shows how to use thetcpdumputility to display all RIPv6 packets.$ tcpdump -s 1500 -envv ipv6 and ether host a:b:c:d:e:f
This example shows how to use the tcpdump utility to display all IPv6 packets arriving at or departing from a host with the Ethernet addressa:b:c:d:e:f
TCPTRACE
TCPTRACE — Traces packets between two hosts.
Syntax
TCPTRACE host [/BUFFERS=n |
/FULL | /OUTPUT=file | /PACKETS=n |
/PORT=option |
/PROTOCOL=option]
Description
TCPTRACE traces packets as they travel between the local and remote host. You can trace all packets or you can use command qualifiers to monitor only those packets of interest.
Qualifiers
- /BUFFERS=n
- Optional. The default is 100. Specifies the number of buffers that TCPTRACE allocates for temporary storage. These buffers must be locked into the working set, so the number can be:
Decreased (to be accommodated in the working set)
Raised (to prevent the dropping of trace packets)
- /FULL
Optional. The default is brief display.
Displays the packet's contents.
- /OUTPUT=file
Optional. The default is screen display. Redirects the output from screen to the specified file. If this file name already exists, the output is appended to it.
- /PACKETS=n
Optional. The default it 10.
Stops the trace after the specified number of packets is displayed.
- /PORT={LOCAL=n | REMOTE=n}
Optional for port number. The default is that all traffic is displayed.
Required for port type. Filters the trace to the specified port.
- /PROTOCOL={ARP | ICMP | IP | TCP | UDP}
Optional. The default is /PROTOCOL=IP.
Filters the specified protocol.
Examples
$ TCPTRACE HOST1 /FULL /PORT=(REMOTE=21)
This example shows how to use the
TCPTRACEcommand to trace packets between the local system andHost1.TCPTRACEfilters all packets except those packets directed to port 21 on the remote host.$ TCPTRACE HOST2 /PORT=(LOCAL=23, REMOTE=1056) - _$ /FULL /PACKETS=30 /OUTPUT=TELNET_TRACE.TXT
This example shows how to use the
TCPTRACEcommand to trace packets between the local system andHost2.TCPTRACEfilters all packets except those packets directed to port 23 on the local host and port 1056 on the remote host. The trace results are output to a file with the name TELNET_TRACE.TXT. The trace stops after 30 packets meeting the specifications are encountered.
traceroute
traceroute — Displays the route that packets take to the network host.
Syntax
traceroute [-m max_ttl] [-n] [-p
port] [-q nqueries] [-r] [-s
src_addr] [-v] [-w waittime]
host [packetsize]
Description
The Internet is a large and complex aggregation of network hardware connected
together by gateways. The traceroute command tracks the route that
packets follow from gateway to gateway. The command uses the IP protocol
time-to-live (TTL) field and attempts to elicit an ICMP TIME_EXCEEDED response from
each gateway along the path to a particular host.
The only mandatory parameter is the destination host name or IP address. The
default probe datagram length is 38 bytes, but you can increase this value by
specifying a packet size (in bytes) after the destination host name. This is useful
when the -f option is given for MTU discovery along the route. You
should start with the maximum packet size for your own network interface (if the
given value is even bigger, traceroute attempts to select a more
appropriate value). If no packet size is given when using the -f
option, traceroute determines the initial MTU automatically. To track
the route of an IP packet, traceroute launches UDP probe packets with a
small TTL (time-to-live) and then listens for an ICMP “time exceeded”
reply from a gateway. Probes start with a TTL of 1 and increment by one until either
an ICMP “port unreachable” is returned (indicating that the packet
reached the host) or until the maximum number of hops is exceeded (the default is 30
hops and can be changed with the -m option). At each TTL setting, three
probes are launched (the number can be changed with the -q option), and
traceroute displays a line showing the TTL, address of the gateway,
and round-trip time of each probe. If the probe answers come from different
gateways, traceroute displays the address of each responding system. If
there is no response within a 3-second timeout interval (which can be changed with
the -w option), traceroute displays an asterisk (*) for
that probe.
-p option.Note
This program is intended for use in network testing, measurement, and
management. It should be used primarily for manual fault isolation. Because
of the load it could impose on the network, do not use
traceroute during normal operations or from automated
scripts.
Flags
- -A
Looks up the AS-number (autonomous system) for each hop's network address at the
whoisserver specified by the-hoption.- -a
If the destination host has multiple addresses,
tracerouteprobes all addresses if this option is set. Normally, only the first address as returned by the resolver is attempted.- -c stoptime
Specifies a delay (in seconds) to pause between probe packets. This can be necessary if the final destination is a router that does not accept undeliverable packets in bursts.
- -f
Disables IP fragmentation. If the given packet size is too big to be handled unfragmented by a machine along the route, a “fragmentation needed” status is returned, and the indicator !F is printed. If a gateway returns the proper MTU size to be used,
tracerouteautomatically decreases the packet size to this new value. If the proper MTU size is not returned,traceroutechooses a smaller packet size.- -g gateway
Enables the IP LSRR (loose source record route) option. This is useful for asking how somebody at the specified gateway reaches a particular target.
- -h server
Specifies the name or IP address of the
whoisserver that is contacted for the AS-number lookup, if the-Aoption is given.- -i initial_ttl
Sets the starting time-to-live value to
initial_ttl, to override the default value of 1. Effectively this skips processing for intermediate hosts that are less thaninitial_ttlhops away.- -k
Keeps the connection to the
whoisserver permanently open. This speeds lookups considerably, because a connection setup for each individual lookup is not necessary. However, not allwhoisservers support this feature.- -l
Prints the value of the TTL field in each packet received. (This flag can be used to help detect asymmetric routing.)
- -m max_ttl
Sets the maximum time-to-live (maximum number of hops) used in outgoing probe packets. The default is 30 hops, which is the same default used for TCP connections.
- -N
Displays the network name for each hop. If a BIND resolver cannot be reached, network names are retrieved just from the
/etc/networksfile.- -n
Displays the hop IP addresses using dotted-decimal notation. This saves a name server address-to-name lookup for each gateway found on the path. It also prevents a reverse lookup for numeric dotted-quad addresses given on the command line, such as destination
hostor-g gatewayaddresses.- -p port
Sets the base UDP port number used in probes. (The default value is 33434.) The
traceroutecommand presumes that nothing is listening on UDP portsbasetobase+nhops-1at the destination host (so an ICMP “port unreachable” message is returned to terminate the route tracing). If another process is listening on a port in the default range, use this option to pick an unused port range.- -Q maxquit
Stops probing this hop after the number of consecutive timeouts specified by
maxquitare detected. The default value is 5. Useful in combination with-Sif you have specified a bignqueriesprobe count.- -q nqueries
Sets the number of probes launched at each TTL setting. The default is 3.
- -r
Bypasses the normal routing tables and sends directly to a host on an attached network. If the host is not on a directly attached network, an error is returned. This option can be used to ping a local host through an interface that has no route through it (for example, after the interface was dropped by ROUTED or GATED).
- -S
Prints a summary of per-hop minimum/average/maximum rtt (round-trip time) statistics. This flag suppresses the per-probe rtt and TTL reporting. To obtain more detailed statistics, increase the default
nqueriesprobe count. For more information, see also theeoption.- -s src_addr
Uses the following IP address (which must be given as an IP number, not as a host name) as the source address in outgoing probe packets. On hosts with more than one IP address, this option can be used to force the source address to be something other than the IP address of the interface on which the probe packet is sent. If the IP address is not one of this machine's interface addresses, an error is returned and nothing is sent.
- -v
Lists any received ICMP packets other than TIME_EXCEEDED and UNREACHABLE.
- -w waittime
Sets the time (in seconds) to wait for a response to a probe. The default is 3 seconds.
Parameters
- host
Specifies the name or IP address of the destination host. This parameter is required.
- packetsize
Specifies the default length for a probe datagram. This parameter is optional. The default is 38 bytes.
Examples
traceroute command.localhost> traceroute nis.nsf.net traceroute to nis.nsf.net (35.1.1.48), 30 hops max, 56 byte packet 1 helios.ee.lbl.gov (128.3.112.1) 19 ms 19 ms 0 ms 2 lilac-dmc.Berkeley.EDU (128.32.216.1) 39 ms 39 ms 19 ms 3 lilac-dmc.Berkeley.EDU (128.32.216.1) 39 ms 39 ms 19 ms 4 ccngw-ner-cc.Berkeley.EDU (128.32.136.23) 39 ms 40 ms 39 ms 5 ccn-nerif22.Berkeley.EDU (128.32.168.22) 39 ms 39 ms 39 ms 6 128.32.197.4 (128.32.197.4) 40 ms 59 ms 59 ms 7 131.119.2.5 (131.119.2.5) 59 ms 59 ms 59 ms 8 129.140.70.13 (129.140.70.13) 99 ms 99 ms 80 ms 9 129.140.71.6 (129.140.71.6) 139 ms 239 ms 319 ms 10 129.140.81.7 (129.140.81.7) 220 ms 199 ms 199 ms 11 nic.merit.edu (35.1.1.48) 239 ms 239 ms 239 ms
This
traceroutecommand displays the route that packets take to a remote host. In this example, note that display lines 2 and 3 are identical. This is due to a bug in the kernel on the second hop system,lbl-csam.arpa, that forwards packets with a zero TTL. (This is a bug in the distributed version of BSD Version 4.3.)localhost> traceroute allspice.lcs.mit.edu traceroute to allspice.lcs.mit.edu (18.26.0.115), 30 hops max 1 helios.ee.lbl.gov (128.3.112.1) 0 ms 0 ms 0 ms 2 lilac-dmc.Berkeley.EDU (128.32.216.1) 19 ms 19 ms 19 ms 3 lilac-dmc.Berkeley.EDU (128.32.216.1) 39 ms 19 ms 19 ms 4 ccngw-ner-cc.Berkeley.EDU (128.32.136.23) 19 ms 39 ms 39 ms 5 ccn-nerif22.Berkeley.EDU (128.32.168.22) 20 ms 39 ms 39 ms 6 128.32.197.4 (128.32.197.4) 59 ms 119 ms 39 ms 7 131.119.2.5 (131.119.2.5) 59 ms 59 ms 39 ms 8 129.140.70.13 (129.140.70.13) 80 ms 79 ms 99 ms 9 129.140.71.6 (129.140.71.6) 139 ms 139 ms 159 ms 10 129.140.81.7 (129.140.81.7) 199 ms 180 ms 300 ms 11 129.140.72.17 (129.140.72.17) 300 ms 239 ms 239 ms 12 * * * 13 128.121.54.72 (128.121.54.72) 259 ms 499 ms 279 ms 14 * * * 15 * * * 16 * * * 17 * * * 18 ALLSPICE.LCS.MIT.EDU (18.26.0.115) 339 ms 279 ms 279 ms
In this example, gateways 12, 14, 15, 16, and 17 either do not send ICMP “time exceeded” messages or send them with a TTL too small to reach the local host. Further investigation is required to determine the cause. For example, by contacting the system administrators for gateways 14 through 17, you could discover that these gateways are running the MIT C Gateway code that does not send “time exceeded” messages.
A fully qualified domain name is a name that ends with a dot (.), as in host.domain.