Cisco 7600 Series Router Software Configuration Guide, Cisco IOS Release 15S
Unknown Unicast Flood Blocking
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Table of Contents

Unknown Unicast Flood Blocking

Understanding UUFB

Configuring UUFB

Unknown Unicast Flood Blocking

This chapter describes how to configure the unknown unicast flood blocking (UUFB) feature on the Cisco 7600 series routers.


Note For complete syntax and usage information for the commands used in this chapter, refer to the Cisco 7600 Series Routers Command References at this URL:

http://www.cisco.com/en/US/products/hw/routers/ps368/prod_command_reference_list.html


 

Understanding UUFB

Unknown unicast traffic is flooded to all Layer 2 ports in a VLAN. You can prevent this behavior by using the UUFB feature. The UUFB feature blocks unknown unicast traffic flooding and only permits egress traffic with MAC addresses that are known to exit on the port. The UUFB feature is supported on all ports that are configured with the switchport command, including private VLAN (PVLAN) ports.

Configuring UUFB

To configure UUFB, perform this task:

 

Command
Purpose

Step 1

Router# configure terminal

Enters global configuration mode.

Step 2

Router(config)# interface {{ type 1 slot/port } | { port-channel number }}

Selects the interface to configure.

Step 3

Router(config-if)# switchport block unicast

Enables UUFB on the port.

Step 4

Router(config-if)# do show interfaces [ type 1 slot/port ] switchport | include unicast

Verifies the configuration.

1.type = ethernet, fastethernet, gigabitethernet, or tengigabitethernet

This example shows how to configure UUFB on Fast Ethernet port 5/12 and how to verify the configuration:

Router# configure terminal
Router(config)# interface fastethernet 5/12
Router(config-if)# switchport block unicast
Router(config-if)# do show interface fastethernet 5/12 switchport | include unicast

Unknown unicast blocked: enabled