Web Management Guide

Chapter 11 | Security Measures
Configuring Port Security
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Configuring Port Security
Use the Security > Port Security page to configure the maximum number of device
MAC addresses that can be learned by a switch port, stored in the address table,
and authorized to access the network.
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 address
table will be 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.
Command Usage
◆ The default maximum number of MAC addresses allowed on a secure port is
zero (that is, disabled). To use port security, you must configure the maximum
number of addresses allowed on a port.
◆ To configure the maximum number of address entries which can be learned on
a port, and then specify the maximum number of dynamic addresses allowed.
The switch will learn up to the maximum number of allowed address pairs
<source MAC address, VLAN> for frames received on the port. When the port
has reached the maximum number of MAC addresses, the port will stop
learning new addresses. The MAC addresses already in the address table will be
retained and will not be aged out.
Note that you can manually add additional secure addresses to a port using the
Static Address Table (page 163).
◆ When the port security state is changed from enabled to disabled, all
dynamically learned entries are cleared from the address table.
◆ If port security is enabled, and the maximum number of allowed addresses are
set to a non-zero value, any device not in the address table that attempts to use
the port will be prevented from accessing the switch.
◆ If a port is disabled (shut down) due to a security violation, it must be manually
re-enabled from the Interface > Port > General page (page 103).
◆ A secure port has the following restrictions:
■
It cannot be used as a member of a static or dynamic trunk.
■
It should not be connected to a network interconnection device.
■
RSPAN and port security are mutually exclusive functions. If port security is
enabled on a port, that port cannot be set as an RSPAN uplink port, source
port, or destination port. Also, when a port is configured as an RSPAN
uplink port, source port, or destination port, port security cannot be
enabled on that port.