System information

Troubleshooting ISO CLNS
Book Title
12-286
ISO CLNS: Poor Performance
Symptom: Users experience poor performance or sudden loss of connections. One or more routers
might be receiving duplicate routing updates and might see routers and ESs on multiple interfaces.
Table 12-9 outlines the problems that might cause this symptom and describes solutions to those
problems.
Table 12-9 ISO CLNS: Poor Performance
Redistribution feedback
loop
exists
Redistribution between an IS-IS cloud and an ISO-IGRP cloud should be performed
only at a single point. If it is not, routing information can be advertised back into one of
the clouds, causing routing feedback loops.
Examples:
The following example illustrates redistribution of ISO-IGRP routes of Michigan and
ISO-IGRP routes of Ohio into the IS-IS area tagged USA:
router isis USA
redistribute iso-igrp Michigan
redistribute iso-igrp Ohio
The following example illustrates redistribution of IS-IS routes of France and ISO-IGRP
routes of Germany into the ISO-IGRP area tagged Backbone:
router iso-igrp Backbone
redistribute isis France
redistribute iso-igrp Germany
If you must redistribute at another point, use default metrics to perform the redistribution
in one direction only.
Refer to the Cisco IOS Network Protocols Configuration Guide, Part 2 and Network
Protocols Command Reference, Part 2 for information about adjusting ISO CLNS
default metrics.
Possible Problem Solution
Multiple ISO-IGRP
processes are
configured on a
single interface
Step 1 Use the show clns interface exec command to view the interface configuration.
Look for multiple ISO-IGRP processes that are configured on a single interface.
Step 2 If multiple ISO-IGRP processes are configured on a single interface, different
Level 2 updates are being sent out through the same interface.
Multiple Level 2 updates on the same interface can cause congestion problems,
especially if the network is large and links are flapping outside the damping
intervals. Flapping is a routing problem where an advertised route between two
nodes alternates (flaps) back and forth between two paths due to a network problem
that causes intermittent interface failures.
Step 3 Remove one of the ISO-IGRP processes from the interface configuration using the
appropriate no clns router iso-igrp interface configuration command.
Bridge or repeater
in parallel with
router
A bridge or repeater in parallel with a router can cause updates and traffic to be seen from
both sides of an interface.
Step 1 Use the show clns is-neighbors detail and the show clns neighbors detail exec
commands to see through which routers and protocols the router’s adjacencies were
learned.
Possible Problem Solution