Using DSL as a backup for a T1

Unanswered Question

Has anyone had any luck with this setup? I remember trying it a number of years ago with no luck, don't really remember the details it was so long ago.

Any sample configs would be appreciated.

I would have one router with both the T1 and DSL interfaces in it. The T1 would be the standard path for traffic but if the T1 went down I'd like the traffic to move to the DSL.

Thanks in advance!

I have this problem too.
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Paolo Bevilacqua Mon, 05/10/2010 - 08:10

That is routinely done, do you have a reliable network technician to configure it for you ?

Richard Burts Wed, 05/19/2010 - 07:00


I am going to make a couple of assumptions about your environment and assuming that my assumptions are correct I will make a suggestion about what you can do to use DSL as backup to T1.

I am assuming that your router that has both T1 and DSL has both interfaces configured and active. And I am assuming that your router has a static default route pointing out the T1 interface. (if the DSL is not configured and active (you can ping the next hop out the DSL interface) then this is a different problem and we need more information to be able to give you good suggestions. and if the default route is learned by some routing protocol then we need more information about that.)

As long as both interfaces are working and the default route is a static default route then my suggestion is this:

configure a floating static default route using the next hop out the DSL interface as the next hop in the floating static route. It might look something like this:

ip route x.x.x.x 250

x.x.x.x is the next hop out the DSL interface and 250 is the weight of the floating static route.



DialerString_2 Wed, 05/19/2010 - 07:40

Echo Rburst on the default route.  I 'assume' the DSL will be used as a backup to bring up a site-to-site vpn tunnel. I have multiple locations configured this way.

Is the ISP using Bridging or PPPOE? Do you have a static or dynamic ip address? Is the DSL going to bring up a VPN connection back to HQ?

stonnet72 Wed, 05/19/2010 - 10:16

I would suggest getting another router of smaller capacity and plugging in your DSL circuit into that line. You can have the DSL and the router plugged into the switch and once the router link fails then the traffic can be routed out the DSL. This way you are eliminating a single point of failure scenario.


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