C
ONFIGURING
THE
S
WITCH
3-84
Configuring Port Security
Port security is a feature that allows you to configure a switch port with
one or more device MAC addresses that are authorized to access the
network through that port.
When port security is enabled on a port, the switch stops learning new
MAC addresses on the specified port when it has reached a configured
maximum number. Only incoming traffic with source addresses already
stored in the dynamic or static address table will be accepted as authorized
to access the network through that port. If a device with an unauthorized
MAC address attempts to use the switch port, the intrusion will be
detected and the switch can automatically take action by disabling the port
and sending a trap message.
To use port security, specify a maximum number of addresses to allow on
the port and then let the switch dynamically learn the <source MAC
address, VLAN> pair for frames received on the port. Note that you can
also manually add secure addresses to the port using the Static Address
Table (page 3-145). When the port has reached the maximum number of
MAC addresses the selected port will stop learning. The MAC addresses
already in the address table will be retained and will not age out. Any other
device that attempts to use the port will be prevented from accessing the
switch.
Command Usage
• A secure port has the following restrictions:
- It cannot use port monitoring.
- It cannot be a multi-VLAN port.
- It cannot be used as a member of a static or dynamic trunk.
- It should not be connected to a network interconnection device.
• The default maximum number of MAC addresses allowed on a secure
port is zero. You must configure a maximum address count from 1 -
1024 for the port to allow access.
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