Cisco Catalyst 3120 Command Reference Guide

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Cisco Catalyst Blade Switch 3120 for HP Command Reference
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Chapter 2 Cisco Catalyst Blade Switch 3120 for HP Cisco IOS Commands
switchport block
switchport block
Use the switchport block interface configuration command on the switch stack or on a standalone switch
to prevent unknown multicast or unicast packets from being forwarded. Use the no form of this command
to allow forwarding unknown multicast or unicast packets.
switchport block {multicast | unicast}
no switchport block {multicast | unicast}
Syntax Description
Defaults Unknown multicast and unicast traffic is not blocked.
Command Modes Interface configuration
Command History
Usage Guidelines By default, all traffic with unknown MAC addresses is sent to all ports. You can block unknown multicast
or unicast traffic on protected or nonprotected ports. If unknown multicast or unicast traffic is not
blocked on a protected port, there could be security issues.
Blocking unknown multicast or unicast traffic is not automatically enabled on protected ports; you must
explicitly configure it.
For more information about blocking packets, see the software configuration guide for this release.
Examples This example shows how to block unknown multicast traffic on an interface:
Switch(config-if)# switchport block multicast
You can verify your setting by entering the show interfaces interface-id switchport privileged EXEC
command.
Related Commands
multicast Specify that unknown multicast traffic should be blocked.
unicast Specify that unknown unicast traffic should be blocked.
Release Modification
12.2(40)EX This command was introduced.
Command Description
show interfaces switchport Displays the administrative and operational status of a switching
(nonrouting) port, including port blocking and port protection settings.

Cisco Catalyst 3120 Specifications

General

Brand	Cisco
Model	Catalyst 3120
Category	Switch
Language	English