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Community Member

Is this possible?

Is there any way in IOS to use a ping to a specific IP address as a keepalive? I am trying to implement a failover between two ISP connections without using BGP. I want the connection to switch to the backup if Layer 3 reachibility is lost, not when the Layer1 or Layer2 link fails.

Incoming traffic is not important, so there is no need to announce a specific subnet. The outgoing traffic will be nat'ed to an address on the outbound gateway device, so return traffic will traverse that link.

I know that there are other products that will do this, but don't know of a way in IOS.

Thanks for your help

Community Member

Re: Is this possible?

So I assume you don't have any routing protocols at all running and will be using static routes.

You can just use a weighted static route for your backup link.

The router will only insert a route if the next hop is alive. So if your primary link fails the route will get removed and the weighted route will get inserted.

ip route

ip route 250

Community Member

Re: Is this possible?

I do not know of a way to do this, either. However, With co-operation of your ISP, there are several possibilities.

One would be to use a GRE tunnel and floating static routes. The Tunnel uses TCP keep-alive, and would provide a L3 way to tell if the path to your ISP was functional.

Another way would be to have your ISP send you a host route in any convenient routing protocol. You could then use a route map / Default information originate based on the existence of this route. Most of the IGP routing protocols will do this.

A third way to consider would be to run ODR, and allow CDP to discover the next hop on the ISP network. I would have to try that before I was sure it would work, and the ISP would have to have Cisco routers.

Good luck.


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