Installation guide

Cisco HWIC-4ESW and HWIC-D-9ESW EtherSwitch Interface Cards
How to Configure EtherSwitch HWICs
67
Cisco IOS Release 12.3(8)T4
OL-6454-01
Each VLAN maintains its own logical address table. A known address in one VLAN is unknown in
another until it is learned or statically associated with a port in the other VLAN. An address can be
secure in one VLAN and dynamic in another. Addresses that are statically entered in one VLAN must
be static addresses in all other VLANs.
Changing the Address Aging Time
Dynamic addresses are source MAC addresses that the switch learns and then drops when they are not
in use. Use the Aging Time field to define how long the switch retains unseen addresses in the table. This
parameter applies to all VLANs.
Configuring the Aging Time
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 global configuration mode, follow these steps to configure the dynamic address table aging
time.
SUMMARY STEPS
1. configure terminal
2. mac-address-table aging-time seconds
3. end
DETAILED STEPS
Verifying Aging-Time Configuration
Use the show mac-address-table aging-time command to verify configuration:
Router# show mac-address-table aging-time
Command Purpose
Step 1
Router(config)# configure terminal
Enters global configuration mode.
Step 2
Router(config)# mac-address-table
aging-time seconds
Enters the number of seconds that dynamic addresses are to be
retained in the address table. Valid entries are from 10 to 1000000.
Step 3
Router(config)# end
Returns to privileged EXEC mode.