Information Technology Reference
In-Depth Information
Table 12-7 outlines the problems that might cause this symptom and describes solutions to those
problems.
Table12-7 ISO CLNS: Users Cannot Make Connections over Parallel Path
Possible Problem
Solution
Routing has not
converged
1.
Use the
show clns route
privileged exec command to view
the CLNS routing table. Examine the table for routes listed
as “possibly down.” This indicates that the routing protocol
has not converged.
2.
Wait for the routing protocol to converge. Use the
show clns
route
command again to see whether the routes are now up.
Note:
ISO-IGRP does load balancing only for domain prefix
routes. If you are doing Level 1 or Level 2 routing in ISO-IGRP,
only a single path is maintained. If that path goes down, you must
wait for the network to converge before the alternate path is
available.
Misconfigured
access list
1.
Use the
trace
exec command to determine the path taken to
reach remote hosts.
2.
If you discover a router that is stopping traffic, use the
show
access-lists
privileged exec command to see whether any
access lists are configured on the router.
3.
Disable all access lists on the router using
no access-group
interface configuration commands on the appropriate
interfaces.
4.
Determine whether hosts can now use the protocol in
question. If traffic can get through, it is likely that an access
list is blocking protocol traffic.
5.
Make sure the access list does not filter traffic from ports that
are used by the protocol in question. Configure explicit
permit
statements for traffic that you want the router to
forward normally.
6.
Enable the access list and verify that the protocol still
functions correctly. If problems persist, continue isolating
and analyzing access lists on all routers in the path from
source to destination.
continues
Hardware or
media problem
For information on troubleshooting hardware problems, see
Chapter 3. “Troubleshooting Hardware and Booting Problems.”
For information on troubleshooting media problems, refer to the
media troubleshooting chapter that covers the media type used in
your network.
ISO CLNS: Redistribution Causes Routing Problems
Symptom:
Route redistribution does not work properly and causes routing problems. Traffic does not
get through a router that is redistributing routes between two different routing areas or
domains—typically IS-IS and ISO-IGRP. Observed symptoms range from poor performance to no
communication at all.
