Cisco Systems 2960-S, 2960 Configuring Port Security

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Catalyst 2960 and 2960-S Switch Software Configuration Guide

OL-8603-09

Chapter 23 Configuring Port-Based Traffic Control

Configuring Port Security

The default is to not block flooding of unknown multicast and unicast traffic out of a port, but to flood

these packets to all ports.

Note The interface can be a physical interface or an EtherChannel group. When you block multicast or unicast

traffic for a port channel, it is blocked on all ports in the port-channel group.

Beginning in privileged EXEC mode, follow these steps to disable the flooding of unicast packets and

Layer 2 multicast packets out of an interface:

To return the interface to the default condition where no traffic is blocked and normal forwarding occurs

on the port, use the no switchport block {multicast | unicast} interface configuration commands.

This example shows how to block unicast and Layer 2 multicast flooding on a port:

Switch# configure terminal

Switch(config)# interface gigabitethernet0/1

Switch(config-if)# switchport block multicast

Switch(config-if)# switchport block unicast

Switch(config-if)# end

Configuring Port Security

You can use the port security feature to restrict input to an interface by limiting and identifying MAC

addresses of the stations allowed to access the port. When you assign secure MAC addresses to a secure

port, the port does not forward packets with source addresses outside the group of defined add resses. If

you limit the number of secure MAC addresses to one and assign a single secure MAC address, the

workstation attached to that port is assured the full bandwidth of the port.

Command Purpose

Step 1 configure terminal Enter global configuration mode.

Step 2 interface interface-id Specify the interface to be configured, and enter interface

configuration mode.

Step 3 switchport block multicast Block unknown multicast forwarding out of the port.

Note Only pure Layer 2 multicast traffic is blocked. Multicast

packets that contain IPv4 or IPv6 information in the

header are not blocked.

Step 4 switchport block unicast Block unknown unicast forwarding out of the port.

Step 5 end Return to privileged EXEC mode.

Step 6 show interfaces interface-id switchport Verify your entries.

Step 7 copy running-config startup-config (Optional) Save your entries in the configuration file.