HP OpenVMS Systems Documentation
HP TCP/IP Services for OpenVMS
Tuning and Troubleshooting
Order Number: AA--RN1VB--TE
This manual provides information about how to isolate the causes of network problems and how to tune the TCP/IP Services software for the best performance.
Revision/Update Information: This manual supersedes the Compaq TCP/IP Services for OpenVMS Tuning and Troubleshooting, Version 5.1.
Software Version: HP TCP/IP Services for OpenVMS Version 5.4
Operating Systems: HP OpenVMS Alpha Versions 7.3-1 and 7.3-2
© Copyright 2003 Hewlett-Packard Development Company, L.P.
UNIX® is a trademark of The Open Group.
The information contained herein is subject to change without notice. The only warranties for HP products and services are set forth in the express warranty statements accompanying such products and services. Nothing herein should be construed as constituting an additional warranty. HP shall not be liable for technical or editorial errors or omissions contained herein.
Proprietary computer software. Valid license from HP required for possession, use or copying. Consistent with FAR 12.211 and 12.212, Commercial Computer Software, Computer Software Documentation, and Technical Data for Commercial Items are licensed to the U.S. Government under vendor's standard commercial license.
The HP TCP/IP Services for OpenVMS documentation is available on CD-ROM.
The HP TCP/IP Services for OpenVMS product is the HP implementation of the TCP/IP networking protocol suite and internet services for HP OpenVMS Alpha and HP 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 HP TCP/IP Services for OpenVMS Management manual.
See the HP TCP/IP Services for OpenVMS Installation and Configuration manual for information about installing, configuring, and starting this product.
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.
This manual contains the following two chapters and appendix:
Table 1 lists the documents available with this version of TCP/IP Services.
For additional information about HP OpenVMS products and services, visit the following World Wide Web address:
For a comprehensive overview of the TCP/IP protocol suite, refer to the book Internetworking with TCP/IP: Principles, Protocols, and Architecture, by Douglas Comer.
HP welcomes your comments on this manual. Please send comments to either of the following addresses:
How to Order Additional Documentation
For information about how to order additional documentation, visit the following World Wide Web address:
The name TCP/IP Services means both:
In addition, please note that all IP addresses are fictitious.
The following conventions may be used in this manual:
$ 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.
The second step is to reduce the problem to its basic components and to systematically identify what is and what is not working. Ask the following questions:
The following steps can help you isolate your problem and determine a solution.
Table 1-1 summarizes the tools you use to obtain information about network operations. The following sections describe each tool in detail.
|arp||Controls and displays ARP tables.|
|dig||Sends domain name query packets to name servers.|
|ifconfig||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.|
|ndc||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.|
|netstat||Displays network statistics of sockets, data link counters, specified protocols or aliases, network interfaces, and a host's routing table.|
|nslookup||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.|
|ping||Indicates a host is reachable, and displays statistics about packet loss and delivery time.|
|route||Allows the user to manipulate the network routing tables manually.|
|sysconfig||Displays and maintains the various network subsystem attributes.|
|sysconfigdb||Manages the subsystem configuration database.|
|tcpdump||Provides dump analysis and packet tracing.|
|TCPTRACE||Traces packets going in and out of the system. To run the trace utility, enter the DCL command TCPTRACE.|
|traceroute||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 command procedure. This procedure defines each tool as a foreign command.
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.
When using the 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.
If you do not receive output similar to that shown in the example, then one of the following conditions may exist:
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.
If the remote host does not respond to the request, the ping command displays the following message:
TCPIP> ping a7u1kt ping: unknown host a7u1kt %SYSTEM-F-UNREACHABLE, remote node is not currently reachable
If you used an IP address in the 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
These error messages could indicate that:
The following sample shows the ping statistics displayed:
TCPIP> ping chester PING chester (188.8.131.52): 56 data bytes 64 bytes from 184.108.40.206: icmp_seq=0 ttl=64 time=0 ms 64 bytes from 220.127.116.11: icmp_seq=1 ttl=64 time=1 ms 64 bytes from 18.104.22.168: icmp_seq=2 ttl=64 time=0 ms 64 bytes from 22.214.171.124: 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).