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Backup Internet Routing

I have two locations, each with their own individual Internet connection via DSL.  They are also connected to one another via wireless WAN.  Each location has a Cisco 2841 router with one interface connected to the DSL connection and the other interface connected to the wireless wan.   I want to setup a backup Internet route on each router so that if one the locations loses its DSL Internet connection it can automatically route traffic destined for the Internet over the wireless lan and out the other locations DSL connection.   I'm pretty sure this is possible, so can anyone assist me with this?

I've attached a simple drawing of the network.



Re: Backup Internet Routing

you may use two default route with diffrent admenstrative distance

ip route

ip route 5

the second defualt route will not be used unless the local internet link is failed ( i am assuming you are using defautl routes for internet connectivity)

good luck

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Re: Backup Internet Routing

Agree with marwanshawi about routing and in your case of DSL Internet connection, there will be private IP Addresses in the LAN and if both locations use different IP Address range.

then you need to think about NAT also.

**As there is no supporting data about topology & uploaded drawing is also not very helpful , there are some assumptions


Location A

LAN IP Address -

Location B

LAN IP Address -

you need to make sure that at both location DSLs have NAT configuration for both LAN IP range.


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Re: Backup Internet Routing


Since your two routers are connected together, you would need to run IBGP between your routers and EBGP with your service provide. This will provide failover for you in case one of the locations go down.

Have a look at this document for examples and configurations:



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