Specifications

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Cisco ME 3400 Ethernet Access Switch Command Reference
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Chapter 2 Cisco ME 3400 Ethernet Access Switch Cisco IOS Commands
switchport block
switchport block
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}
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.
If the port is a user network interface (UNI) or enhanced network interface (ENI), you must use the no
shutdown interface configuration command to enable it before using the switchport block command.
UNIs and ENIs are disabled by default. Network node interfaces (NNIs) are enabled by default.
Blocking unknown multicast or unicast traffic is not automatically enabled on protected ports; you must
explicitly configure it.
Note 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.
multicast Specify that unknown multicast traffic should be blocked.
unicast Specify that unknown unicast traffic should be blocked.
Release Modification
12.2(25)EX This command was introduced.