Cisco Systems 78-11741-02 manual Configuring Basic BGP Features, Enabling BGP Routing, IPC-297

Configuring BGP

Configuring Basic BGP Features

Configuring Basic BGP Features

The tasks described in this section are for configuring basic BGP features.

Enabling BGP Routing

To enable BGP routing and establish a BGP routing process, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1
	Router(config)# router bgp as-number	Enables a BGP routing process, which places the
		router in router configuration mode.
Step 2
	Router(config-router)# network network-number[mask	Flags a network as local to this autonomous system
	network-mask][route-maproute-map-name]	and enters it to the BGP table.

Note For exterior protocols, a reference to an IP network from the network router configuration command controls only which networks are advertised. This behavior is in contrast to IGP, such as IGRP, which also use the network command to determine where to send updates.

Note The network command is used to inject IGP routes into the BGP table. The network-maskportion of the command allows supernetting and subnetting. The resources of the router, such as configured NVRAM or RAM, determine the upper limit of the number of network commands you can use. Alternatively, you could use the redistribute router configuration command to achieve the same result.

Configuring BGP Neighbors

Like other EGPs, BGP must completely understand the relationships it has with its neighbors. Therefore, this task is required.

BGP supports two kinds of neighbors: internal and external. Internal neighbors are in the same autonomous system; external neighbors are in different autonomous systems. Normally, external neighbors are adjacent to each other and share a subnet, while internal neighbors may be anywhere in the same autonomous system.

To configure BGP neighbors, use the following command in router configuration mode:

Command	Purpose
Router(config-router)# neighbor {ip-address peer-group-name}	Specifies a BGP neighbor.
remote-as as-number

See the “BGP Neighbor Configuration Examples” section at the end of this chapter for an example of configuring BGP neighbors.

Cisco IOS IP Configuration Guide

IPC-297