Cisco Systems 3750E manual Configuring Port Security, Default Port Blocking Configuration, 26-7

Chapter 26 Configuring Port-Based Traffic Control

Configuring Port Security

Default Port Blocking Configuration

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.

Blocking Flooded Traffic on an Interface

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 multicast and unicast packets out of an interface:

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

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 multicast flooding on a port:

Switch# configure terminal

Switch(config)# interface gigabitethernet1/0/1

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 addresses. 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.

If a port is configured as a secure port and the maximum number of secure MAC addresses is reached, when the MAC address of a station attempting to access the port is different from any of the identified secure MAC addresses, a security violation occurs. Also, if a station with a secure MAC address configured or learned on one secure port attempts to access another secure port, a violation is flagged.

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

OL-9775-02 26-7