[nsp] Is default failover in dual-homed DSL possible?

[Mark Boolootian]

Folks,

I'm looking for a solution for home/business DSL users who want dual-homed 
DSL connections to protect against outages.  The basic picture looks like
this:


       ----------         -----------
       |  ISP 1 |         |  ISP 2  |
       ----------         -----------
           |                    |
           |                    |
           |                    |
          -----               -----
          |   |               |   |  <- DSL modems
          -----               -----
             \               / 
             ----------------
             |   router     |
             ----------------
                    |
                    |
            --------------------

The router is doing NAT, and there is no dynamic routing protocol running
between the router and the ISPs (i.e. typical home DSL setup).  The question
is, are there any products/mechanisms for allowing a static default pointing
at one ISP to failover to the other ISP in the event of a network outage
at the first ISP?

In the above diagram, a failure with DSL would take down the PPP connection,
so presumably if the DSL modem were built-in to the router, the router would
notice that the PPP connection was down, and perhaps the right thing could be 
made to happen.  Unfortunately, I don't know of a small router that would 
accommodate this solution.  I suppose if one were to terminate each DSL 
connection in an individual router, and then feed both those connections into 
a third router, one might be able to manufacture something that would work, 
but I don't think I'd want to put that on my resume (much less mention it on 
this list).

In order to accomodate failures beyond a dead DSL link, I've got a rather 
messy idea in my head of a box sitting on the LAN pinging nameservers in each 
of the ISP's networks, and making routing changes on the router accordingly.  

Has anyone on this list set up anything to deal with such a situation?

Thanks very much,
mb