Switchport Block - Cisco Catalyst 4500 Series Configuration Manual

Chapter 2

switchport block

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.
Syntax Description
multicast
unicast
Command Default Unknown multicast and unicast traffic are not blocked.
All traffic with unknown MAC addresses is sent to all ports.
Command Modes Interface configuration mode
Command History Release
12.1(19)EW
Usage Guidelines You can block the unknown multicast or unicast traffic on the switch ports.
Blocking the unknown multicast or unicast traffic is not automatically enabled on the switch ports; you
must explicitly configure it.
For more information about blocking the packets, refer to the software configuration guide for this
Note
release.
Examples The following example shows how to block the 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 Command
show interfaces switchport
switchport block {multicast | unicast}
no switchport block {multicast | unicast}
Specifies that the unknown multicast traffic should be blocked.
Specifies that the unknown unicast traffic should be blocked.
Modification
This command was introduced on the Catalyst 4500 series switch.
Catalyst 4500 Series Switch Cisco IOS Command Reference—Release XE 3.9.xE and 15.2(5)Ex
Description
Displays the administrative and operational status of a
switching (nonrouting) port.
switchport block
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