Ccna routing and Switching Complete Study Guide

192.168.1.1 

192.168.2.1 

192.168.2.2 

192.168.1.2 

Lo0: 10.0.0.0 

Lo0: 10.0.1.0 

Lo0: 10.0.2.0 

ISP

R1

R2

---

930

 

Chapter 21 

■

  Wide Area Networks

There are three main steps to configure basic BGP:

1.

  Define the BGP process.

2.

  Establish one or more neighbor relationships.

3.

  Advertise the local networks into BGP.

Define the BGP Process

To start the BGP process on a router, use the 

router bgp 

AS

 command. Each process 

must be assigned a local AS number. There can only be one BGP process in a router, which 

means that each router can only be in one AS at any given time.

Here is an example:

ISP#

config t

ISP(config)#

router bgp ?

<1-65535> Autonomous system number

ISP(config)#

router bgp 1

Notice the AS number can be from 1 to 65,535.

Establish One or More Neighbor Relationships

Since BGP does not automatically discover neighbors like other routing protocols do, 

you have to explicitly configure them using the 

neighbor 

peer-ip-address remote-as 

peer-as-number

 command. Here is an example of configuring the ISP router in Figure 21.25:

ISP(config-router)#