Changing The Address Aging Time; Removing Dynamic Address Entries - Cisco WS-C2955T-12 Software Manual

Managing the MAC Address Tables

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:
Command
Step 1
configure terminal
Step 2 mac-address-table aging-time
seconds
Step 3 end
Step 4
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:
Command
Step 1 configure terminal
Step 2 no mac-address-table dynamic
hw-addr
Step 3 end
Step 4
show mac-address-table
You can remove all dynamic entries by using the clear mac-address-table dynamic command in
privileged EXEC mode.
Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide
6-16
Purpose
Enter global configuration mode.
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.
Return to privileged EXEC mode.
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.
Chapter 6 Configuring the System
78-6511-08