We have 3x sites connected to one another via point to point T1 connections. 2 of the sites also have internet access. The 3rd site must access the internet via one of the other sites and failover to the other site if internet connectivity is lost at the first site. Each of the 3 routers are running EIGRP to advertise the internet subnets, but the internet connections are provided by ASA's. How can I failover the internet connection ?
Perhaps there are some aspects of your situation that I do not yet understand. But if the Internet connection is provided by ASAs I would assume that the routers at those sites would have default routes pointed to the ASA. So it would seem logical to redistribute the default routes into EIGRP and advertise it to the third site. Depending on the metrics the third site will either have two equal cost routes to 0.0.0.0/0 and load share, or it will have a preferred route and a backup route. I am not clear whether you need to have a primary and backup or if 2 equal routes would work. But if you need primary and backup then just manipulate the metric when the routes are redistributed and you can easily produce a primary and backup.
I understand your suggestion, however if the internet is down at one site (internet failure rather than ASA failure), the connection wont failover as the interface on the ASA will still be up.
To address that concern you could use the feature of reliable static routes with object tracking. This gives you the ability to check on reachability of some destination address through the ASA and if the address is not reachable to withdraw it from the routing table. If it is withdrawn from the routing table then EIGRP will withdraw that route from the advertisement to its neighbor. See this link for more information about this feature:
