Load Balancing over BGP

Unanswered Question
May 21st, 2009
User Badges:
  • Bronze, 100 points or more

What is the quickest easiest way to achieve some degree of load balancing with BGP?


The problem is I have a remote site with 2 T1's from diverse providers. One is ATT MPLS and the other is VB MPLS. It is all eBGP, peering to the interfaces. I have tried peering to the loopbacks across the cloud and it resulted in some mean route flapping.


So the short version is that I need more bandwidth and I need to figure out how to leverage the unused T.


router bgp 65221

no synchronization

no bgp log-neighbor-changes

network 10.60.254.144 mask 255.255.255.255

network 10.75.121.0 mask 255.255.255.0

neighbor 12.117.255.117 remote-as 7018

neighbor 12.117.255.117 prefix-list Local out

neighbor 152.162.109.33 remote-as 65000

neighbor 152.162.109.33 prefix-list Local out

neighbor 152.162.109.33 route-map AddAS in

neighbor 152.162.109.33 route-map AddAS out

no auto-summary


route-map AddAS permit 15

set as-path prepend 65221 65221

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Loading.
jim_berlow Thu, 05/21/2009 - 13:01
User Badges:
  • Bronze, 100 points or more

Okay - first things first. I cringe when anyone talks about "load balancing" BGP. It really is a redundancy protocol foremost with some "load sharing" as an after thought.


Now that the disclaimer is out of the way, lets get down to business. Think of inbound and outbound as completely separate tasks. For inbound load sharing, AS-Path prepending is really your best option (often it is the only option). For outbound load balancing, you need to look at what you are receiving from the providers. Are you taking full or partial routes? Or are you simply taking default routes. If you are taking full or partial routes then you *should* have some kind of load sharing happening. If you are taking default routes, then you might just need to help direct traffic within the network to the closest router or figure out some load sharing scheme.


This is probably something you should be working with your providers on. I've seen some providers that will manipulate BGP attributes w/o your knowledge (like remove your prepends when they get it). At the least they may have some ideas about what you can do.


Jim

Actions

This Discussion