More about BGP -- load sharing across equal-cost paths

Suppose you have several equal-bandwidth or equal-cost paths between a pair of routers that want to be BGP neighbors. For example, two or more WAN links between two BGP areas. You want the routers to route over both paths. The thing to do is to use a loopback address for your BGP neighbors. You must also have "ebgp-multihop" configured as well, so BGP will be okay with going to a neighbor that is not on the same subnet as itself.

So, router A (AS 64591) and router B (AS 64592) are connected by a pair of WAN links.

On router A:

int loopback 0
ip address 10.255.255.1 255.255.255.255

router bgp 64591
neighbor 10.254.254.1 remote-as 64592
neighbor 10.254.254.1 update-source loopback 0
neighbor 10.254.254.1 ebgp-multihop


Router B looks similar:

int loopback 0
ip address 10.254.254.1 255.255.255.255

router bgp 64592
neighbor 10.255.255.1 remote-as 64591
neighbor 10.255.255.1 update-source loopback 0
neighbor 10.255.255.1 ebgp-multihop

Don't forget to include your loopback network range in the "network" statement for the BGP instance.