Information Technology Reference
In-Depth Information
Table9-6
AppleTalk: Network Services Intermittently Unavailable (continued)
Possible Problems
Solution
Route flapping
(unstable route)
(continued)
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.
4.
If routes are being aged incorrectly, use the
appletalk timers
global configuration command to correct
the problem. Suggested timer values are 10, 30, and 90 to
start, but do not exceed 10, 40, and 120. The first number
must always be 10, and the third value should be three times
the second.
You can return the timers to their defaults (10, 20, 60) by using
the
no appletalk timers
global configuration command.
Timers should be consistently set to the same value throughout
the internetwork, or at a minimum, throughout the backbone of
the internetwork.
ZIP storm
A ZIP storm occurs when a router propagates a route for which
it currently has no corresponding zone name; the route is then
propagated by downstream routers.
Note:
Cisco routers provide a firewall against ZIP storms in the
internetwork. If a Cisco router receives a routing update from a
neighbor, it does not propagate that new route until it receives
the accompanying zone name.
1.
Use the
show appletalk traffic
command to check the field
showing the number of ZIP requests:
Router#
sh apple traffic
[...]
ZIP: 44 received, 35 sent, 6 netinfo
[...]
Router#
Compare this output with the output shown by the command
30 seconds later.
2.
If the traffic counters for ZIP requests are incrementing
very rapidly (by more than 10 every 30 seconds) a ZIP
storm is probably occurring.
