In BGP multihoming environment using 2 routers, you might find that your incoming traffic is fully utilizing one of your 2 links while the other is almost idle. we want to make load sharing on the 2 links for the incoming traffic, and we have control only on our AS.
Please check topology attached.
One of the 2 EBGP links is fully utilized by incoming traffic while the other is almost idle, so there is waste of the resources that is not being used.
In order to solve this phenmenon, we should advertise some of our networks using AS prepending while the others without, and on the other router we should do the same but with the other networks..
For Example: as in the attached topology we have 4 networks in our AS 188.8.131.52, 184.108.40.206, 220.127.116.11 and 18.104.22.168. In RT1 we can advertise the network 20 and 30 normally while advertising the network 40 and 50 using AS prepending by using routing policy..
In RT2 we can advertise the network 40 and 50 normally while advertising the network 20 and 30 using AS prepending by routing policy.
This is because you are advertising all of your networks through both links, and at the point where the 2 routes are received there is always one of them preferred than the other.
At RT5 check the bgp route table and you will find that network 20 & 30 have a path while the network 40 & 50 have the other path..