2 ISPs Failover configuration

[strny0007]

Hello,

I am trying to configure the failover scenario:

I have 2 ISPs. The first one is ADSL connected to ADSL router and then to cisco router, which I configure. The second one has a public IP address with subnet mask /30. The problem is that when I configure failover by tracking the gateway on the second ISP then I am not able to recognize not working connection, because the gateway still responses to a ping, but some next router on the way is not working, so the route remains in routing table and "internet connection" does not work.

My idea is if I ping some IP address in the internet, than I am able to recognize not working connection. But if tried this it does not work, because tracked IP address is not in my network, so from tracking routine it is unreachable anyway. Any idea how to do it?

Thanks,

Pavel

[Vivek Ganapathi]

Hello Pavel,

You need to have two default routes. One pointed to your primary internet Service. Another with a higher metric to second service. You need to track the Primary internet service. To do this, you may prefer to perform icmp-echo to an internet based IP (for example : 4.2.2.2 or 8.8.8.8). You would then, create one more static route to have 4.2.2.2 or 8.8.8.8 pointed to your primary internet service. The reason to have this route pointed to Primary internet is that when your primary path comes back online, you must re-route automatically via your primary internet provider.

Hope this clears.

Regards

Vivek

[strny0007]

Thanks, I will try it.

Regards

Pavel

[Rick Morris]

If you only put in a track ip ping echo with no static route for where that ping should go then it will choose any connection based on the routing table.  What you must do is something like the following.

ISP A is connected to Gig1/0

ISP B is connected to Gig2/0

you will want to have 2 static route for the IP you plan on pinging on the internet to track the status of an interface.

ip route 4.1.1.1 255.255.255.255 x.x.x.x

ip route 4.2.2.2 255.255.255.255 x.x.x.x

This link provides some good instructions on what to do and why.

http://docwiki.cisco.com/wiki/IP_SLA_Tracking_with_Configuration_Example

[cadet alain]

Hi,

You could also use local PBR to be sure your IP SLA ping test will always take the primary path or specify the source-interface in the IP SLA echo command.

Regards.

Alain

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