Cisco WS-C2950T-24 Software Guide - Page 144

Managing the MAC Address Tables Chapter 6 Configuring the System Changing the Address Aging Time Dynamic addresses are source MAC addresses that the switch learns and then drops when they are not in use. The aging time parameter defines how long the switch retains unseen addresses in the table. This parameter applies to all VLANs. Setting too short an aging time can cause addresses to be prematurely removed from the table. Then when the switch receives a packet for an unknown destination, it floods the packet to all ports in the same VLAN as the receiving port. This unnecessary flooding can impact performance. Setting too long an aging time can cause the address table to be filled with unused addresses; it can cause delays in establishing connectivity when a workstation is moved to a new port. Beginning in privileged EXEC mode, follow these steps to configure the dynamic address table aging time: Step 1 Step 2 Step 3 Step 4 Command Purpose configure terminal Enter global configuration mode. mac-address-table aging-time seconds Enter the number of seconds that dynamic addresses are to be retained in the address table. You can enter a number from 10 to 1000000. end Return to privileged EXEC mode. show mac-address-table aging-time Verify your entry. Removing Dynamic Address Entries Beginning in privileged EXEC mode, follow these steps to remove a dynamic address entry: Step 1 Step 2 Step 3 Step 4 Command configure terminal no mac-address-table dynamic hw-addr end show mac-address-table Purpose Enter global configuration mode. Enter the MAC address to be removed from dynamic MAC address table. Return to privileged EXEC mode. Verify your entry. You can remove all dynamic entries by using the clear mac-address-table dynamic command in privileged EXEC mode. 6-16 Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide 78-6511-08