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Catalyst 3750 Switch Software Configuration Guide
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Chapter 24 Configuring Port-Based Traffic Control
Configuring Port Security
Configuration Guidelines
Follow these guidelines when configuring port security:
• Port security can only be configured on static access ports or trunk ports. A secure port cannot be a
dynamic access port.
• A secure port cannot be a destination port for Switched Port Analyzer (SPAN).
• A secure port cannot belong to a Fast EtherChannel or a Gigabit EtherChannel port group.
• You cannot configure static secure or sticky secure MAC addresses in the voice VLAN.
Note Voice VLAN is only supported on access ports and not on trunk ports, even though the
configuration is allowed.
• A secure port cannot be a private-VLAN port.
• When you enable port security on an interface that is also configured with a voice VLAN, you must
set the maximum allowed secure addresses on the port to two plus the maximum number of secure
addresses allowed on the access VLAN. When the port is connected to a Cisco IP phone, the IP
phone requires up to two MAC addresses. The IP phone address is learned on the voice VLAN and
might also be learned on the access VLAN. Connecting a PC to the IP phone requires additional
MAC addresses.
• If any type of port security is enabled on the access VLAN, dynamic port security is automatically
enabled on the voice VLAN. You cannot configure port security on a per-VLAN basis.
• When a voice VLAN is configured on a secure port that is also configured as a sticky secure port,
all addresses on the voice VLAN are learned as dynamic secure addresses, and all addresses seen on
the access VLAN to which the port belongs are learned as sticky secure addresses.
• When you enter a maximum secure address value for an interface, and the new value is greater than
the previous value, the new value overwrites the previously configured value. If the new value is less
than the previous value and the number of configured secure addresses on the interface exceeds the
new value, the command is rejected.
• The switch does not support port security aging of sticky secure MAC addresses.
Enabling and Configuring Port Security
Beginning in privileged EXEC mode, follow these steps to restrict input to an interface by limiting and
identifying MAC addresses of the stations allowed to access the port:
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Enter interface configuration mode, and enter the physical interface to
configure.
Step 3
switchport mode {access | trunk} Set the interface switchport mode as access or trunk; an interface in the
default mode (dynamic auto) cannot be configured as a secure port.
Step 4
switchport port-security Enable port security on the interface.
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