Leaflet

OL-11615-01

Catalyst 6500 Unknown Unicast Flood Blocking (Cisco IOS)

In Catalyst 6500 Series switches running Cisco IOS software, the unicast flood blocking feature is called

Unknown Unicast Flood Blocking (UUFB).

By default, all the Layer 2 ports on the switch are configured to allow unicast flooding.

To block unicast flooding on Layer 2 ports, perform the following steps:

Step 1 Enter global configuration mode and select the interface to configure.

Router# configure terminal

Router(config)# interface {{

type slot/port

} | {port-channel number}}

Step 2 Enable Unknown unicast flood blocking on the port using the switchport block unicast command.

Router(config-if)# switchport block unicast

This example shows how to configure UUFB on Fast Ethernet port 5/12:

Router# configure terminal

Router(config)# interface fastethernet 5/12

Router(config-if)# switchport block unicast

For more information on unknown unicast flood blocking on the Catalyst 6500 running Cisco IOS, refer

to the following URL:

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/122sx/swcg/blocking.htm

Catalyst 4500 Port Unicast and Multicast Flood Blocking (Cisco IOS)

Catalyst 4500 Series switches running Cisco IOS software support port unicast and multicast flood

blocking. As the name indicates, this feature is capable of blocking multicast floods in addition to

unicast floods. By default, all the ports on the switch are configured to allow unicast and multicast

flooding. Unicast flood blocking and multicast flood blocking can be enabled independently.

To block unicast or multicast flooding on switch ports, perform the following steps:

Step 1 Enter global configuration mode and select the interface to configure.

Switch# configure terminal

Switch(config)# interface

interface-id

Step 2 Enable unicast flood blocking on the port using the switchport block unicast command.

Switch(config-if)# switchport block unicast

Step 3 Enable multicast flood blocking on the port using the switchport block multicast command.

Switch(config-if)# switchport block multicast

This example shows how to block unicast and multicast flooding on a GigabitEthernet interface1/1:

Switch# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Switch(config)# interface gigabitethernet1/1

Switch(config-if)# switchport block multicast