Configuring Next-Hop Processing; Next Hops - Juniper JUNOSE 11.2.X BGP AND MPLS Configuration Manual

Configuring Next-Hop Processing

Copyright © 2010, Juniper Networks, Inc.
Select the path received from the peer with the lowest BGP router ID.
11.
Select the path that was learned from the neighbor with the lowest peer remote
12.
address.
The following sections discuss the attributes evaluated in the path decision process.
Examples show how you might configure these attributes to influence routing decisions.
Routes sent by BGP speakers include the next-hop attribute. The next hop is the IP
address of a node on the network that is closer to the advertised prefix. Routers that
have traffic destined for the advertised prefix send the traffic to the next hop. The next
hop can be the address of the BGP speaker sending the update or of a third-party node.
The third-party node does not have to be a BGP speaker.
The next-hop attributes conform to the following rules:
The next hop for EBGP sessions is the IP address of the peer that advertised the route.
The next hop for IBGP sessions is one of the following:
If the route originated inside the AS, the next hop is the IP address of the peer that
advertised the route.
If the route originated outside the AS—that is, it was injected into the AS by means
of an EBGP session—the next hop is the IP address of the external BGP speaker that
advertised the route.
For routes advertised on multiaccess media—such as Frame Relay, ATM, or
Ethernet—the next hop is the IP address of the originating router's interface that is
connected to the medium.

Next Hops

If you use the neighbor remote-as command to configure the BGP neighbors, the next
hop is passed according to the rules provided above when networks are advertised.
Consider the network configuration shown in Figure 28 on page 106. Router Jackson
advertises 192.168.22.0/23 internally to router Memphis with a next hop of 10.2.2.1. Router
Jackson advertises the same network externally to router Topeka with a next hop of
10.1.13.1.
Chapter 1: Configuring BGP Routing
105