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6500 - MAC address table slow to display or missing


When I look up a MAC address using 'show mac-adress-table dynamic' the switch takes around four minutes to respond, sometimes providing the MAC address table, other times reporting:

'MAC entries unavailable, please try later!'

and sometimes doing both.

This has only recently started happening; switch CPU rarely goes above 15% and the table holds around 2000 MAC addresses, of which 500 are static. Normal switching appears to be unaffected.


Anyone have any ideas how I can start troubleshooting this slow reponse issue?


Thanks in advance






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Cisco Employee

The default ARP table aging

The default ARP table aging time is 4 hours while the CAM holds the entries
for only 5 minutes. The switch sends out a frame to all forwarding ports
within the respective VLAN when the destination MAC address is aged out from
the CAM table. You need a CAM aging timer greater or equal to the ARP
timeout in order to prevent unicast flooding. As a workaround, you can issue
one of the command in order to increase the CAM aging timer for the VLAN you
are having trouble with to match the ARP aging time:


Issue the" mac-address-table again-time"

ml#wp1085773> mac-address-table aging-time command and I would like you to
monitor this situation and let me know the results.


In case if that doesnt resolve might be some issue with your SUp module.





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