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HP OpenVMS Systems Documentation

HP TCP/IP Services for OpenVMS

Tuning and Troubleshooting

Order Number: AA--RN1VB--TE

September 2003

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

Hewlett-Packard Company Palo Alto, California

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.

ZK6631

The HP TCP/IP Services for OpenVMS documentation is available on CD-ROM.

Contents

Index

Preface

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.

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.

Document Structure

This manual contains the following two chapters and appendix:

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.

Reader's Comments

HP welcomes your comments on this manual. Please send comments to either of the following addresses:

Internet	openvmsdoc@hp.com
Postal Mail	Hewlett-Packard Company OSSG Documentation Group, ZKO3-4/U08 110 Spit Brook Rd. Nashua, NH 03062-2698

How to Order Additional Documentation

For information about how to order additional documentation, visit the following World Wide Web address:

http://www.hp.com/go/openvms/doc/order

Conventions

The name TCP/IP Services means both:

HP TCP/IP Services for OpenVMS Alpha
HP TCP/IP Services for OpenVMS VAX

In addition, please note that all IP addresses are fictitious.

The following conventions may be used in this manual:

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.
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.
`[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.
...	A horizontal ellipsis in examples indicates one of the following possibilities: Additional optional arguments in a statement have been omitted. The preceding item or items can be repeated one or more times. Additional parameters, values, or other information can be entered.
. . .	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.
( )	In command format descriptions, parentheses indicate that you must enclose choices in parentheses if you specify more than one.
[ ]	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.
\|	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.
{ }	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.
bold type	Bold type represents the introduction of a new term. It also represents the name of an argument, an attribute, or a reason.
italic type	Italic type 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).
`Example`	This typeface indicates code examples, command examples, and interactive screen displays. In text, this type also identifies URLs, UNIX commands and pathnames, PC-based commands and folders, and certain elements of the C programming language.
UPPERCASE TYPE	Uppercase type indicates a command, the name of a routine, the name of a file, or the abbreviation for a system privilege.
-	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.
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

The inability to reach remote hosts and networks is usually caused by one of the following:

Physical connection failure
Underlying transport failure (UDP, TCP, IP)
Incorrectly configured routing, applications, or services such as BIND
User error

1.2 Isolating Problems

The first step in problem isolation is to make sure that the TCP/IP Services product is started. This may seem like an obvious step, but it is frequently overlooked because error messages may not indicate the product is disabled. (Instead, the messages returned may be "invalid host" or something similar.) You may not have stopped the product, but someone else may have. To check whether the product is running, enter the following command:

$ 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:

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?

The following steps can help you isolate your problem and determine a solution.

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.

Table 1-1 summarizes the tools you use to obtain information about network operations. The following sections describe each tool in detail.

**Table 1-1 Diagnostic Tools**
Diagnostic Tool	Function
`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.

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.

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:

TCP/IP Services may not be running.
A definition for localhost is 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.

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:

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.

The following sample shows the 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).