Changing The Address Aging Time; Removing Dynamic Address Entries - Cisco Catalyst 2950 Software Manual

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
Step 1
configure terminal
Step 2
mac-address-table aging-time
seconds
Step 3
end
Step 4
show mac-address-table
aging-time

Removing Dynamic Address Entries

Beginning in privileged EXEC mode, follow these steps to remove a dynamic address entries:
Command
Step 1 configure terminal
Step 2
clear mac-address-table
dynamic [address mac-addr |
interface interface-id | vlan
vlan-id]
Step 3
end
Step 4
show mac-address-table
Catalyst 2950 Desktop Switch Software Configuration Guide
6-16
Purpose
Enter global configuration mode.
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.
Return to privileged EXEC mode.
Verify your entry.
Purpose
Enter global configuration mode.
(Optional) Enter the address mac-addr to delete the specified MAC
address.
(Optional) Enter the interface interface-id to delete all dynamic
MAC addresses on the specified physical port or port channel.
(Optional) Enter the vlan vlan-id to delete all dynamic MAC
addresses for the specified VLAN. Valid IDs are from 1 to 1005; do
not enter leading zeroes.
Return to privileged EXEC mode.
Verify your entry.
Chapter 6 Configuring the System
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