Chapter 21. TCP/IP Problem Analysis
This chapter is intended to be used for determining solutions to problems
encountered while using TCP/IP.This chapter contains:
vGeneral information for determining problems regardless of what application you
are using. Youare given the following information:
– A chart of potential problems.
– A cause list for each potential problem in the chart.
vInformation for determining problems with PING, SLIP,TELNET, FTP, SMTP,the
POP server, the HTTPserver, the workstation gateway server, LPR, and LPD.
The debugging information for sockets is available in
Sockets Programming
,
SC41-5422-03. The debugging information for the SNMP agent is available in

Simple Network Management Protocol (SNMP) Support

, SC41-5412-00. For
TELNET,FTP, SMTP, the POP server,LPR, and LPD, you are given one or more
of the following:
– A chart of potential problems.
– A cause list for each potential problem in the chart.
– A description for tracing the TCP/IPapplication.
– A description of the materials required for reporting TCP/IPproblems.
The following steps should be followed when finding causes and solutions for
TCP/IP problems:
1. Follow the flow chart in Figure 247on page 431 to verify the connectivity
between the local and remote systems.
2. Once you verify connectivity, determine which section of this document to go to
based on what area the problem is occurring in. For example, if the problem is
in SMTP,go to the section “Determining Problems for SMTP” on page 457.
3. Read the section associated with the function where the problem is occurring.
4. Use the flow chart provided to isolate the problem, if possible.
5. Find the cause list for that potential problem.
6. Follow the cause list instructions for correcting the problem.
7. Obtain the debugging materials required for reporting the problem if none of the
actions in the cause list corrects the problem. This might include a trace of the
function when the problem occurs. Instructions for collecting a communications
trace are provided in “Collecting a Communications Trace”on page 493.
Note: All reported TCP/IP problems should include a copy of the configuration files
used for TCP/IP processing.
Toobtain a copy of the TCP/IP configuration files do the following:
1. If you have not created the library IBMLIB or output queue IBMOUTQ, enter the
following commands:
CRTLIB LIB(IBMLIB)
CRTOUTQ OUTQ(IBMLIB/IBMOUTQ)
2. Enter the following commands to add the library IBMLIB to your library list and
to change the output queue for your job to output queue IBMOUTQ:
ADDLIBLE IBMLIB
CHGJOB * OUTQ(IBMLIB/IBMOUTQ)
© Copyright IBM Corp. 1997, 1999 429
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