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Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide
OL-8915-03
Chapter 5 Administering the Switch
Managing the MAC Address Table
When private VLANs are configured, address learning depends on the type of MAC address:
•
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.
For more information about private VLANs, see
Chapter 14, “Configuring Private VLANs.”
Default MAC Address Table Configuration
Table 5-3
shows the default MAC address table configuration.
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:
Table 5-3
Default MAC Address Table Configuration
Feature
Default Setting
Aging time
300 seconds
Dynamic addresses
Automatically learned
Static addresses
None configured
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
mac address-table aging-time
[
0
|
10-1000000
] [
vlan
vlan-id
]
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.
Step 3
end
Return to privileged EXEC mode.
Step 4
show mac address-table aging-time
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
