6-53
Catalyst 3550 Multilayer Switch Software Configuration Guide
78-11194-03
Chapter6 Administering the Swi tc h Managing the MAC Address Table
Default MAC Address Table Configuration
Table 6 -4 shows the default MAC address table configuration.
Changing the Address Aging Time
Dynamic addresses are source MAC addresses that the switch learns and t he n a ge s wh en th ey ar e no t in
use. You can change the aging time setting for all VLANs or for a specified VLAN.
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 c an i m pact per fo rmanc e . Set ti ng t oo long an
aging time can cause the address table to be filled with unused addresses, w hich prevents new addresses
from being learned. Flooding results, which can impact switch performance.
Beginning in privileged EXEC mode, follow these steps to c onfi gure t he dy na mic a ddr ess tab le ag ing
time:
To return to the default value, use the no mac-address-table aging-time global configuration command.
Table6-4 Default MAC Address Table Configuration
Feature Default Setting
Aging time 300 seconds
Dynamic addresses Automatically learned
Static addresses None configured
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 mac-address-table aging-time [0 |
10-1000000] [vlan vlan-id]Set the length of time that a dynamic entry remains in the MAC
address table after the entry is used or updated.
The range is 10 to 1000000 seconds. The default is 300. You can also
enter 0, which disables aging. Static address entries are never aged
or removed from the table.
For vlan-id, valid IDs are 1 to 1005.
Step3 end Return to privileged EXEC mode.
Step4 show mac-address-table aging-time Verify your entries.
Step5 copy running-config startup-config (Optional) Save your entries in the configuration file.