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We have a single public /24 subnet, with a BGP router as the primary gateway. Now I'm interested in configuring a second router for redundancy.

How do I deal with multiple gateways on the servers in our public subnet?

I found some other questions related to multiple gateways that seem to deal with NAT set-ups. In my situation, the servers all have public routed IP-addresses. So from what I can tell, it doesn't really matter which route incoming or outgoing packets take.

But I figure the servers need some way of telling when one of the gateways is down, and route around it? Is this accomplished with protocols such as OSPF? And do I need to deploy this on all my servers?

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I'm still interested in solutions to this. I'm beginning to think OSPF is overkill and not really the solution. (I also still don't understand it.) So now I'm leaning towards something installed on all machines (no problem, really) that ping-monitors routers and reconfigures routes as necessary. Is there anything existing that does this? –  Shtééf Sep 20 '10 at 14:52
    
With OSPF you can set priorities on routers. This allows you to create a BDR (Backup Designated Router) which will be used if your Designated Router goes down. You won't have to install it on your servers, only your routers must support it. –  Cocoabean May 27 '11 at 7:29

1 Answer 1

You want to look into HSRP and tracking. It depends how you will define 'gateway is down' - look into http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a0080094e8c.shtml.

Or, if you have 2 routers and they're running BGP, just use HSRP between them, and if router 1 loses its link to the internet (BGP goes down), if it is the active HSRP router, it will just send all the packets to router 2 because it doesn't have a better route.

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