Default Mac Address Table Configuration; Changing The Address Aging Time - Cisco Catalyst 2950 Software Configuration Manual

Managing the MAC Address Table

Default MAC Address Table Configuration

Table 7-4
Table 7-4
Feature
Aging time
Dynamic addresses
Static addresses

Changing the Address Aging Time

Dynamic addresses are source MAC addresses that the switch learns and then ages when they are not 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 can impact performance. Setting too long an
aging time can cause the address table to be filled with unused addresses, which prevents new addresses
from being learned. Flooding results, which can impact switch performance.
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 [0 |
10-1000000] [vlan vlan-id]
Step 3
end
Step 4
show mac-address-table aging-time
Step 5 copy running-config startup-config
To return to the default value, use the no mac-address-table aging-time global configuration command.
Catalyst 2950 Desktop Switch Software Configuration Guide
7-54
shows the default MAC address table configuration.

Default MAC Address Table Configuration

Default Setting
300 seconds
Automatically learned
None configured
Purpose
Enter global configuration mode.
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 4094 when the enhanced software
image is installed and 1 to 1005 when the standard software image is
installed. Do not enter leading zeros.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Chapter 7 Administering the Switch
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