Configuration Guide User guide

1342 FastIron Configuration Guide

53-1002494-02

BGP4 overview

• RFC 2842 (Capability Advertisement)

• RFC 3065 (BGP4 Confederations)

To display BGP4 configuration information and statistics, refer to “Displaying BGP4 information” on

page 1421.

NOTE

Your Layer 3 switch management module must have 32 MB or higher to run BGP4.

BGP4 overview

Border Gateway Protocol 4 (BGP4) is the standard Exterior Gateway Protocol (EGP) used on the

Internet to route traffic between Autonomous Systems (AS) and to maintain loop-free routing. An

autonomous system is a collection of networks that share the same routing and administration

characteristics. For example, a corporate intranet consisting of several networks under common

administrative control might be considered an AS. The networks in an AS can but do not need to

run the same routing protocol to be in the same AS, nor do they need to be geographically close.

Routers within an AS can use different Interior Gateway Protocols (IGPs) such as RIP and OSPF to

communicate with one another. However, for routers in different autonomous systems to

communicate, they need to use an EGP. BGP4 is the standard EGP used by Internet routers and

therefore is the EGP implemented on Brocade Layer 3 switches.

Figure 166 on page 1342 shows a simple example of two BGP4 autonomous systems. Each AS

contains three BGP4 switches. All of the BGP4 switches within an AS communicate using IBGP.

BGP4 switches communicate with other autonomous systems using EBGP. Notice that each of the

switches also is running an Interior Gateway Protocol (IGP). The switches in AS1 are running OSPF

and the switches in AS2 are running RIP. Brocade Layer 3 switches can be configured to

redistribute routes among BGP4, RIP, and OSPF. They also can redistribute static routes.

FIGURE 166 Example BGP4 autonomous systems

AS 1

AS 2

EBGP

IBGP

OSPF

IBGP

OSPF

RIP

IBGP

BGP4 Switch