8-23
Catalyst2950 and Catalyst2955 Switch Software Configuration Guide
78-11380-10
Chapter8 Administering the Swi tc h Managing the MAC Address Table
Default MAC Address Table Configuration
Table 8 -3 shows the default MAC address table configuration.
Changing the Address Aging Time
Dynamic addresses are source MAC addresses that the switch learn s a nd th en ag es wh en th e y ar e n ot i n
use. The aging time parameter defines how long the switch retains unseen addresses. 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 unkno wn desti nation, it floods the p acket to all ports in the same
VLAN as the receiving port. This unnecessary flooding can imp act per for manc e. Set ti ng t oo long an
aging time can cause the address table to be filled with unused addresses, which prevents new addresses
from being learned.
Beginning in privileged EXEC mode, follow these steps to configure the dynamic address table aging
time:
To return to the default value, use the no mac addr ess-table aging-time global configuration command.
Table8-3 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]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.
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.