Cisco Cisco Gigabit Ethernet Switch Module (CGESM) for HP Technical References

Use the switchport block interface configuration command 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}

Unknown multicast and unicast traffic is not blocked.

Interface configuration

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 Cisco Gigabit Ethernet Switch Module for HP 
p-Class BladeSystem Software Configuration Guide for this release.

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.

Specify that unknown multicast traffic should be blocked.

Specify that unknown unicast traffic should be blocked.

12.2(25)SE1

This command was introduced.

Displays the administrative and operational status of a switching port, 
including port blocking and port protection settings.