3Com Switch 8800 Advanced Software V5 Configuration Guide

Configuring MAC Address Table Management 65
Disabling Global MAC
Address Learning
You may need to disable MAC address learning sometimes to prevent the MAC
address table from being saturated, for example, when your device is being
attacked by a great deal of packets with different source MAC addresses.
Disabling the global MAC address learning disables the learning function on all
ports.
Follow these steps to disable MAC address learning:
Disabling MAC Address
Learning on an Ethernet
Port or Port Group
After enabling global MAC address learning, you may disable the MAC address
learning function on a port as needed.
Follow these steps to disable MAC address learning on a port or port group:
Configuring MAC
Address Aging Timer
The MAC address table on your device is available with an aging mechanism for
dynamic entries to prevent its resources from being exhausted. Set the aging timer
appropriately: a long aging interval may cause the MAC address table to retain
outdated entries and fail to accommodate latest network changes; a short interval
may result in removal of valid entries and hence unnecessary broadcasts which
may affect device performance.
Follow these steps to configure the MAC address aging timer:
To do... Use the command... Remarks
Enter system view system-view -
Disable global MAC address
learning
mac-address mac-learning
disable
Required
Enabled by default
To do... Use the command... Remarks
Enter system
view
system-view -
Enable global MAC
address learning
undo mac-address mac-learning
disable
Optional
Enabled by default.
Enter
Etherne
t
interfac
e view
or port
group
view
Enter Ethernet
interface view
interface interface-type
interface-number
Use either command
In Ethernet interface
view, the following
configurations only
take effect for the
current port; in port
group view, the
configurations take
effect for all ports.
Enter port
group view
port-group { aggregation agg-id |
manual port-group-name}
Disable MAC address
learning on an Ethernet
interface or port group
mac-address mac-learning disable Required
Enabled by default
To do... Use the command... Remarks
Enter system view system-view -
Set the aging timer for
dynamic MAC address entries
mac-address timer { aging
seconds | no-aging }
Optional
300 seconds by default.