Specifications

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Catalyst 4500 Series Switch Cisco IOS Command Reference—Release IOS XE 3.3.0XO(15.1(1)XO)
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Chapter 2 Cisco IOS Commands for the Catalyst 4500 Series Switches
switchport block
switchport bloc k
To prevent the unknown multicast or unicast packets from being forwarded, use the switchport block
interface configuration command. To allow the unknown multicast or unicast packets to be forwarded,
use the no form of this command.
switchport block {multicast | unicast}
no switchport block {multicast | unicast}
Syntax Description
Defaults U nknown multicast and unicast traffic are not blocked.
All traffic with unknown MAC addresses is sent to all ports.
Command Modes Interface configuration mode
Usage Guidelines You can bl ock the unknown multicast or unicast traffic on the switch ports.
Blocking the unknow n multicast or unicast traffic is not automatically enabled on the switch ports; you
must explicitly configure it.
Note For more information about blocking the packets, refer to the sof tware configuration guide for this
release.
Examples This exampl e shows how to block the unknown mu lticast 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 Spec ifies that the un known mu lticast t raffic should be bloc ked.
unicast Specifies that the unknown unicast traffic should be blocked.
Command Description
show interfaces switchport Displays the administrative and operational status of a
switching (nonrouting) port.