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Common AppleTalk Troubleshooting Issues

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When troubleshooting ZIP storms, use the show appletalk traffic

command. Evidence of a storm can be found by reviewing the number of ZIP
requests over a period of 30 seconds, and noting a higher than normal incre-
ment. Although debug commands can provide further troubleshooting
information, it is recommended that a protocol analyzer be used. This is
because of the high processor utilization that the debug command requires
and other network issues that are usually associated with ZIP storms.

Higher than normal assumes that the administrator has established a baseline

for the network. This is a troubleshooting step that occurs before an incident. By

comparing the network when it is operating correctly to the degraded network

metrics, a course of action should become clear.

AARP Broadcast Frames

When connecting to an AppleTalk network, the workstation (or other device)
sends AARP probe frames to verify that its address is unique. On Ethernet and
Token Ring, the station sends 10 broadcasts. If there is a response, the workstation
must send another set of AARP broadcasts with a different address to find an
available address. On networks with a low number of available addresses, this can
result in a significant amount of traffic.

Prevention of this problem can be more beneficial than detection. When setting

up networks, make certain that there is sufficient growth room for addresses. If
troubleshooting, use the show appletalk traffic command to review the sta-
tus of AARP broadcast frames.

Phase One/Phase Two Compatibility Problems

Although this problem is very unlikely in most modern networks, the
differences between the versions of the AppleTalk protocol can create
significant service disruptions.

The Cisco IOS has supported phase two since version 8.2, and few admin-

istrators have any reason to not use phase two throughout the network. How-
ever, it is possible that a legacy or misconfigured router can cause a phase one/
phase two mismatch. The show appletalk globals command provides the
administrator with a simple method of troubleshooting this potential cause. If
the show appletalk globals command reports incompatibility with a phase
one device, the show appletalk neighbors and show appletalk route
commands should provide sufficient information for resolution.

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