Cisco Systems 15327 Configuring IRB

CHAPTER

12-1

Ethernet Card Software Feature and Configuration Guide, R7.2

January 2009

Configuring IRB

This chapter describes how to configure integrated routing and bridging (IRB) for the ML-Series card.

For more information about the Cisco IOS commands used in this chapter, refer to the

Cisco IOS Command Reference publication.

This chapter includes the following major sections:

• Understanding Integrated Routing and Bridging, page 12-1

• Configuring IRB, page 12-2

• IRB Configuration Example, page 12-3

• Monitoring and Verifying IRB, page 12-4

Caution Cisco Inter-Switch Link (ISL) and Cisco Dynamic Trunking Protocol (DTP) are not supported by the

ML-Series, but the ML-Series broadcast forwards these formats. Using ISL or DTP on connecting

devices is not recommended. Some Cisco devices attempt to use ISL or DTP by default.

Your network might require you to bridge local traffic within several segments and have hosts on the

bridged segments reach the hosts or ML-Series card on routed n etworks. For example, if you are

migrating bridged topologies into routed topologies, you might want to start by co nnecting some of the

bridged segments to the routed networks.

Using the integrated routing and bridging (IRB) feature, you can route a given protocol be tween routed

interfaces and bridge groups within a single ML-Series card. Specifically, local or unroutable traffic is

bridged among the bridged interfaces in the same bridge group, while routable traffic is routed to other

routed interfaces or bridge groups.

Because bridging is in the data link layer and routing is in the network layer, they have different protocol

configuration models. With IP, for example, bridge group interfaces belong to the same network and have

a collective IP network address. In contrast, each routed interface represents a distinct network and has

its own IP network address. Integrated routing and bridging uses the conce pt of a Bridge Group Virtual

Interface (BVI) to enable these interfaces to exchange packets for a given protocol.

A BVI is a virtual interface within the ML-Series card that acts like a normal routed interface. A BVI

does not support bridging but actually represents the corresponding bridge group to routed interfaces

within the ML-Series card. The interface number is the link between the BVI and the bridge group.

Before configuring IRB, consider the following: