Depending on how your network is built, its sometimes is best to increase the aging time of mac-addresses(CAM) to reduce the unnecessary flooding that is caused by the default time out value of 5 minutes. You also have to take caution not to fill up the cam table by having to many stale entries.
CAM—All Catalyst switch models use a CAM table for Layer 2 switching. As frames arrive on switch ports, the source MAC addresses are learned and recorded in the CAM table. The port of arrival and the VLAN are both recorded in the table, along with a timestamp. If a MAC address learned on one switch port has moved to a different port, the MAC address and timestamp are recorded for the most recent arrival port. Then, the previous entry is deleted. If a MAC address is found already present in the table for the correct arrival port, only its timestamp is updated.
Command:
mac address-table aging-time [0 | 10-1000000] [vlan vlan-id]
Verification:
show mac address-table aging-time
Recommended Read:
http://www.techexams.net/forums/ccnp/41520-cam-table-aging.html
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