3Com 7700 Configuration Manual page 225

Perform the following configuration in system view.
Table 15 Set MAC Address Table Entries
Operation
Add/Modify an address entry
Delete an address entry
When deleting the dynamic address table entries, the learned entries will be
deleted simultaneously.
Disable/Enable Global MAC Address Learning
With the address learning function, an Ethernet switch can learn new MAC
addresses. After received a packet destined some already learned MAC address,
the switch will forward it directly with the hardware, instead of broadcasting.
Sometimes for the sake of security, it is necessary to disable the address learning
function. A common threat is from hackers who attack the switch with packets
from different source MAC addresses, thereby exhausting the address table
resources and making it impossible for the switch to update the MAC address
table according to the network changes. Such attack can be avoided by disabling
the MAC address learning function.
You can use the following commands to disable/enable the MAC address learning
globally.
Perform the following configuration in system view.
Table 16 Disable/Enable the MAC Address Learning
Operation
Disable the MAC address learning
Enable the MAC address learning
By default, the MAC address learning function is enabled.
Disable/Enable MAC Address Learning on a Port
After the MAC address learning has been enabled globally, you can disable it on
individual ports.
Use the following commands to disable the MAC address learning on a specified
port.
Perform the following configurations in the ethernet port view.
Table 17 Disable/Enable the MAC Address Learning
Operation
Disable the MAC address learning
Enable the MAC address learning
By default, the MAC address learning function is enabled.
MAC Address Table Management
Command
mac-address { static | dynamic } hw-addr interface {
interface-name | interface-type interface-num }
undo mac-address [ static | dynamic ] [ [ hw-addr ]
interface [interface-name | interface-type interface-num
] ]
Command
mac-address mac-learning disable
undo mac-address mac-learning disable
Command
mac-address mac-learning disable
undo mac-address mac-learning disable
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