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Not all line description types must have a SSAP for TCP/IP so please check
the source service access point (SSAP) list in the line description associated
with the interface as described in Appendix A. Configuring a Physical Line
for TCP/IP Communication.
f. Verify all line description items, particularly the frame size which should be
greater than the maximum transmission unit (MTU) of the interface.
g. If a remote system fails to respond, it may mean that the system, network,
gateway, router, or bridge in the network is unavailable or not working.
Failure to respond can also mean that the remote system does not put into
effect the ICMP echo request protocol. Try verifying the connection to other
systems and between those other systems to determine where the failure is
most likely located.
h. Verify that the local interface configuration and the routing configuration,
described in “Step 2—Configuring a TCP/IP Interface” on page 30 and “Step
3—Configuring TCP/IP Routes” on page 32, is correct.
i. Ensure the following two routing entries are configured in the QSYSWRK
subsystem description if the TCP/IP interfaces, including LOOPBACK, do not
activate or you cannot end or start TCP/IP. If they do not exist, or if they are
not correct, then add or correct them and try the request again.
ADDRTGE SBSD(QSYS/QSYSWRK) +
SEQNBR(2505) +
CMPVAL(TCPIP) +
PGM(QSYS/QTOCTCPI) +
CLS(QSYS/QSYSCLS20) +
MAXACT(*NOMAX) +
POOLID(1)
ADDRTGE SBSD(QSYS/QSYSWRK) +
SEQNBR(2506) +
CMPVAL(TCPEND) +
PGM(QSYS/QTOCETCT) +
CLS(QSYS/QSYSCLS20) +
MAXACT(*NOMAX) +
POOLID(1)
Cause List B
If your VFYTCPCNN or PING commands were successful to the local system, you
should verify the possibility of connecting between your system and the other
system you want to communicate with. Run the PING command as you did
previously, but this time specify the internet address of the remote host. See
“Common Error Messages” on page 438.
1. If you can verify the connection using the remote internet address but not the
remote system name, then the name or address is not correct in your host
table, or the remote name servers may not be available.
2. If your system uses remote name servers, verify that you can reach each
remote name server by using the PING command and specifying the internet
address of the remote name server.
3. When a remote system appears not to respond, it is possible that the system
has responded but the packet was dropped due to a maximum frame size
limitation. For example, if a TCP/IP communications line on the AS/400 system
was configured with a maximum frame size of 576 bytes, an ICMP echo request
sent on that line might preclude receiving an echo reply if the reply exceeded
576 bytes. It may appear to the AS/400 user that the remote host was not
responding even though it had responded properly. Use the additional
parameters of the PING command to decrease the packet length of the PING.
Chapter 21. TCP/IP Problem Analysis 433