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HSRP & multihomed AS running BGP

The ISP I work for is multihomed and running BGP on both links, we also happen to have two 7206vxr's. Currently we have one 7206 as the main border router and the other not connected at all, same config just powered down and sitting there.. I believe this is called a "cold standby router situation", requires manual intervention in case of failure, move cables and such.

In an attempt to utilize our 2nd 7206vxr I've looked into running HSRP and IBGP to provide redundency. I looked that these urls and thought they'd give me some guidance..

The only problem that I see is outbound link utilization. Since the 2nd url mentions that HSRP "has no effect on return traffic" -- inbound traffic would be fine. However, outbound traffic will use serial interface on the active router and the standby router will see very little outbound traffic. Not only could this saturate one links' outbound bandwidth, but result in less then optimal paths. Say the standby router's link has a shorter AS path to a remote network, but because EBGP routes have a preference of 20 and IBGP has a pref of 200, traffic takes a longer path... More hops, latency and sub-optimal routing..

The 2nd url also mentions MHSRP but says that you'd need change settings on the client end, something we'd really like to avoid.

If we had one primary link and a backup link of lesser bandwidth, this would make life easier - but both links have the same amount of bandwidth. We see very good load balancing between both links running on one router.

Does anyone some suggestions on how to load balance outbound traffic between HSRP groups on a multihomed AS running IBGP between the two border routers??

That last sentence was a mouthful........


Re: HSRP & multihomed AS running BGP

MHSRP Would the the best in your scenerio. I am unsure what client changes would need to be made, assuming you've already got more than one internal subnetwork requiring routing. If so, one group could be routed on one of your VXRs and the other could be on the other one. Giving you both outbound load sharing and redundancy.

Hope this helps you,



Re: HSRP & multihomed AS running BGP

Hi grunky,

there is a small error in your reasoning. If the standby router has a route with a shorter AS-path, the primary will learn this route via IBGP and prefer this route over his own (longer path) router. So in that case only the shortest IBGP route will be put in the routing table and will be used.

This is exactly the setup we used at my previous employer and it worked well.



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