System information

Troubleshooting ISO CLNS
Book Title
12-280
Table 12-5 ISO CLNS: Host Cannot Access Hosts in Different Area
Possible Problem Solution
Level 2 routers are not
routing packets to the
correct area
Step 1 Use the trace command to verify that Level 1 routers are routing packets to the
nearest Level 2 router.
Sample Display:
The following display shows an example of ISO CLNS trace output:
router# trace
Protocol [ip]: clns
Target CLNS address: thoth
Timeout in seconds [3]:
Probe count [3]:
Minimum Time to Live [1]:
Maximum Time to Live [30]:
Type escape sequence to abort.
Tracing the route to THOTH
(55.0006.0100.0000.0000.0001.8888.1112.1314.1516)
HORUS(55.0006.0100.0000.0000.0001.6666.3132.3334.3536) 32
msec ! 28 msec
28 msec !
2 ISIS(55.0006.0100.0000.0000.0001.7777.2122.2324.2526)
56 msec ! 80 msec
56 msec !
3 THOTH(55.0006.0100.0000.0000.0001.8888.1112.1314.1516) 80
msec ! 80 msec ! 8
Step 2
Use the trace exec command to verify that Level 2 routers are routing packets to
the correct destination area.
Step 3 If packets are not being routed to the correct area, check the Level 2 routing
tables (ISO-IGRP
1
) or the Level 2 link state databases (IS-IS) to see whether the
packets are being forwarded to another area.
Step 4 If necessary, reconfigure routers with the correct area addresses and Level 2
(IS-IS) routing information.
ES host is not running
ES-IS protocol
Step 1 Use the appropriate host commands to verify that an ES-IS process is running. If
necessary, initiate the ES-IS process on the host.
Step 2 Check the adjacency database on the host and verify that it has an entry for its
directly connected router.
Step 3 Use the debug clns packet privileged exec command on the Level 1 router to
verify that it sees and forwards packets from the ES.
Caution: Because debugging output is assigned high priority in the CPU
process, it can render the system unusable. For this reason, use debug
commands only to troubleshoot specific problems or during troubleshooting
sessions with Cisco technical support staff. Moreover, it is best to use debug
commands during periods of lower network traffic and fewer users. Debugging
during these periods decreases the likelihood that increased debug command
processing overhead will affect system use.
Step 4 If necessary, statically configure the router to recognize the ES by using the clns
es-neighbor interface configuration command.
Route redistribution
problem
Misconfigured route redistribution can cause connectivity problems. For specific
troubleshooting information, see the section “ISO CLNS: Redistribution Causes Routing
Problems” later in this chapter.