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Failover to 2ndary ISP

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dunks59

IS-IT--Management
Feb 12, 2009
9
US
Question on failover routing for a none BGP router.

I have a Cisco 3800 which has 3 interfaces. s1/0 is a DS/3 interface. This is the primary upstream and downstream medium. This has a /30 ip address with the upstream provider, which I don't own. g0/1 connects to a secondary ISP. This is a backup radio link. The IP on this is a /30 with the secondary IP which is advertising the parent subnet via BGP of my network which is on g0/0. The DS/3 provider is only advertising my /24 subnet via BGP. The DS/3 provider is advertising me on the upstream interface so if the psychical interface goes down they stop advertising my subnet. BGP automatically fails over to my secondary ISP as they are adversing the larger subnet to mine.

The situation I'm trying to solve is how do i make it so my 3800 (no running BGP) changes it's default GW to the secondary ISP. Another note is that the secondary ISP is least preferred as it's abt 1/2 the bandwidth so i wld want to switch back to the DS/2 ASAP.

I've talked to a friend of mine abt this and he mentioned that the best way to do this is have a linux box behind the 3800 which would preform the change. The linux box wld be running programs that would constantly be checking to ensure the primary link is alive and packets would make it from and to my network via the primary ISP. If the link failed the linux box would login into the 3800, change the default gw and bring down the DS/3 interface which would in turn have all my traffic run through the secondary ISP.

The above concept looks good to me. The only issue is I don't even know what to google for in order to fine this solution or at least a how-to or s/t tell what i can start with. Does anyone have any idea on this?
 
Hello
First of all it would be clearer if you post as scrub "show run".
In any case,a simple floating static route should do the job.

ip route 0.0.0.0 0.0.0.0 xxx.xxx.xxx.xxx
ip route 0.0.0.0 0.0.0.0 xxx.xxx.xxx.xxx 254 <<<<Higher AD metric

There's another way to do what you want with all on the Cisco router.Don't use the Linux box it will only bring more complexity into the network.
Regards
 
Not sure if this would be a solution for your situation, but we are using a great little applicance that is consolidating bandwidht, handling DNS traffic, and providing automatic failover redundancy without any manual intervention. Very cool stuff!


Jeff
 
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