Category: BGP

MP-eBGP Configuration

Some information on how to configure multiprotocol extended Border Gateway Protocol (MP-EBGP). Extended BGP allows for the transport of routing information for multiple network layer protocols IPv6, VPNv4, and others. MP-BGP allows you to have a unicast routing topology different from a multicast routing topology, which helps to control the network and resources.

In this example, the R1 and R3 routers are configured to be in AS 5500 forming iBGP. The R2 router is configured to be in AS 6500. The R1 and R2 routers communicate with each other using MP-EBGP.

MP-BGP Config

More BGP next-hop-self

From the below you can see the next hop for 192.168.0.0 network is 10.0.0.2 which is outsite of 65000 AS, and router jazz doesn’t have a route to it.  BGP will not put 192.168.0.0 into routing table because it doesn’t know how to reach next hop, you can see this below:

BGP-Next Hp Self 2

BGP-Next Hp Self 3

BGP-Next Hp Self 4

By adding the next-hop-self command on the router owen it will change the next-hop attribute for external networks that will be advertised to the router Jazz:

owen(config-router)#neighbour 10.0.1.2 next-hop-self

BGP-Next Hp Self 4.5

This changes the next hop attribute from 10.0.0.2 to be 10.0.1.1 on the router owen

BGP-Next Hp Self 5

from Jazz you can now ping (192.168.0.1) on Jules.

BGP-Next Hp Self 6

Job done!

eBGP Configuration with a Loopback Address

You can also configure eBGP using a loopback address (or any other operational interface) as shown in this section. Loopback interfaces are used in this manner to guarantee reachability in networks with multiple paths as shown in the Load Sharing Using the Loopback Address as a BGP Neighbor section of Load Sharing with BGP in Single and Multihomed Environments: Sample Configurations.

eBGP Config with a loopback

 

Basic eBGP Configuration

In this configuration, the router owen is in AS 300 and Router jazz is in AS 400.

eBGP Config

Peers must be directly connected when using eBGP.  If they are not directly connected, the neighbor ebgp-multihop command must be used and a path through an IGP or static route to reach the peer must exist in order for the routers to establish neighbor relationship. In the configuration above, owen router belongs to AS 300 while jazz router belongs to AS 400.