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Cisco IE 2000 Switch Software Configuration Guide
OL-25866-01
Chapter 7 Performing Switch Administration
Information About Performing Switch Administration
When private VLANs are configured, address learning depends on the type of MAC addre ss:
Dynamic MAC addresses learned in one VLAN of a private VLAN are replicated in the associated
VLANs. For example, a MAC address learned in a private-VLAN secondary VLAN is replicated in
the primary VLAN.
Static MAC addresses configured in a primary or secondary VLAN are not replicated in the
associated VLANs. When you configure a static MAC address in a private VLAN primary or
secondary VLAN, you should also configure the same static MAC address in all associated VLANs.
Default MAC Address Table ConfigurationAddress Aging Time for VLANs
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.
MAC Address Change Notification Traps
MAC address change notification tracks users on a network by storing the MAC address change activity.
When the switch learns or removes a MAC address, an SNMP notification trap can be sent to the NMS.
If you have many users coming and going from the network, you can set a trap-interval time to bundle
the notification traps to reduce network traffic. The MAC notification history table stores MAC address
activity for each port for which the trap is set. MAC address change notifications are generated for
dynamic and secure MAC addresses. Notifications are not generated for self addresses, multicast
addresses, or other static addresses.
Static Addresses
A static address has these characteristics:
Is manually entered in the address table and must be manually removed.
Can be a unicast or multicast address.
Does not age and is retained when the switch restarts.
Tab l e 7-2 Default MAC Address Table Configuration
Feature Default Setting
Aging time 300 seconds
Dynamic addresses Automatically learned
Static addresses None configured