Mac-Address Timer - 3Com Switch 4500 Family Manual

Use the undo mac-address max-mac-count command to cancel the limitation on the number of MAC
addresses an Ethernet port can learn.
By default, the number of MAC addresses an Ethernet port can learn is unlimited.
When you use the mac-address max-mac-count command, the port stops learning MAC addresses
after the number of MAC addresses it learned reaches the value of the count argument you provided.
You can use the undo command to cancel this limit so that the port can learn MAC addresses without
the number limitation. By default, no number limitation is set to the port for MAC address learning.
To prevent illegal devices from accessing the network through a port, you can configure static MAC
addresses and disable MAC address learning for the port. Thus, only the packets destined for the
configured MAC addresses can be forwarded out the port.
Related commands: mac-address, mac-address timer.
Examples
# Set the maximum number of MAC addresses GigabitEthernet 1/0/3 port can learn to 600.
<Sysname> system-view
System View: return to User View with Ctrl+Z.
[Sysname] interface GigabitEthernet 1/0/3
[Sysname-GigabitEthernet1/0/3] mac-address max-mac-count 600

mac-address timer

Syntax
mac-address timer { aging age | no-aging }
undo mac-address timer aging
View
System view
Parameters
aging age: Specifies the aging time (in seconds) for dynamic MAC address entries. The age argument
ranges from 10 to 1000000.
no-aging: Specifies not to age dynamic MAC address entries.
Description
Use the mac-address timer command to set the MAC address aging timer.
Use the undo mac-address timer command to restore the default.
The default MAC address aging timer is 300 seconds.
The timer applies only to dynamic address entries, including both entries learnt and configured.
Setting an appropriate MAC address aging timer is important for the switch to run efficiently.
If the aging timer is set too short, the MAC address entries that are still valid may be removed.
Upon receiving a packet destined for a MAC address that is already removed, the switch
broadcasts the packet through all its ports in the VLAN which the packet belongs to. This
decreases the operating performance of the switch.
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