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Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide
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Chapter 6 Configuring the System
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:
Removing Dynamic Address Entries
Beginning in privileged EXEC mode, follow these steps to remove a dynamic address entry:
You can remove all dynamic entries by using the clear mac-address-table dynamic command in
privileged EXEC mode.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
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.
Step 3
end
Return to privileged EXEC mode.
Step 4
show mac-address-table aging-time Verify your entry.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
no mac-address-table dynamic
hw-addr
Enter the MAC address to be removed from dynamic MAC address table.
Step 3
end
Return to privileged EXEC mode.
Step 4
show mac-address-table
Verify your entry.