Failover solution using BGP

Austin Wilson austinw at
Wed Dec 31 01:42:43 UTC 2008

If you don't have control over the other site my best advice would be to use the BGP communities your transit providers give you. If you setup your clients routes to a lower Local Perf on your transit provider's network, your transit provider will always pick the primary provider's routes first. The moment the primary site stops announcing the route your transit provider will immediately start announcing yours. This works better then AS prepend because almost all providers override the AS prepend with a higher local pref for free peers, local customers, etc. The only other issue would be, how to stop the primary network from advertising your client's routes automatically. This could be done by the client setting up BGP with the primary provider and then pulling the routes. If your client does not run BGP then it all depends on how the ips are setup on the primary side. My best advice is if they don't have BGP to tell them to set it up. Tell them to setup a private AS BGP session with their provider and just get a default route from them. This way they use just about any piece of networking equipment and they don't need their own external AS. Then they can either shutdown the port, BGP session, or pull the route (all they can do themselves) to have their provider pull the route from the internet.

Use this link to find common communities:

Otherwise, the customer could get around this whole issue by setting up some type global server load balancing. There are quite a few companies that have solutions for this. But it would take a lot more technical networking knowledge on the client side.


-----Original Message-----
From: Naveen Nathan [mailto:naveen at]
Sent: Tuesday, December 30, 2008 5:09 PM
To: nanog at
Subject: Failover solution using BGP


I would appreciate insight and experience for the following situation.

I have a client that would like to announce a /18 & /19 over BGP in
Sacramento and LA, us being the second location in LA. Our location
will be a failover location incase Sacramento goes down.

They want failover for extreme cases when they're completly down in
Sacramento. They have strict requirements so that traffic to their blocks
should exclusively go to Sacramento or LA.

This seems difficult to automate and they are aware of this. They will
contact their provider to stop announcing the blocks and subsequently
contact us to announce their routes.

I am wondering is there a better way to approaching the situation
without resorting to announcing the routes when the client calls us
and tells us to failover. This seems to be the inherent problem aswell
because the customer wants this to be a manual process.

Naveen Nathan

To understand the human mind, understand self-deception. - Anon

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