Allied Telesis AT-S25 - Manual (Page 80)

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Secure
This selection activates port security. With this option selected,
the switch will continue to learn MAC addresses for each port up
to a user-configurable maximum number. Once the maximum
number has been reached on a port, any frames received on the
port from a source with a new MAC addresses will be discarded.
If you select this security feature, all static MAC addresses are
deleted and must be reentered. All static MAC addresses are
included in the count of maximum addresses that can be learned
by a port.
When you select this security level, the following prompts are
displayed:
Figure 34 Secure Port Security Prompts
Select the Config MAC address limit per port option to display a list
of the ports on the switch. In the list, specify the maximum
number of MAC addresses that you want each port to be able to
learn. The permitted range is 0 to 255. Specifying 0 (zero) means
that the port will not stop learning addresses. The default is 0.
The prompts also allow you to control how the switch will
respond when a port exceeds the specified number of MAC
addresses. You can instruct the switch to send an SNMP trap to
the management station or disable the port, or both.
Note
You must reset the stack to activate a change of security level to a
switch in the stack. The new security level will not be activated until
the stack has been reset.