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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.
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.
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