to have a backup default route automatically switch over if the default route is down. My situation is I have 3 separate buildings connected with a fiber ring all using private ip addreess. Each building has an 3550 switch connecting the 3 buildings with the fiber. Then there is a ASA5505 at each location connected to the 3550 switch to reach the internet. If one of the locations looses its internet connection I manually change the default route on the switch to point to one of the other 2 buildings and internet traffic will then pass accross the fiber and out there internet connections. Does the 3550 switch have the ability to monitor or track the ISP default gateway so when its down, the 3550 will switch its default route to a default route with a higher cost.
Similar to this document on the ASA5500 using dual ISP's, document ID 70559
IP tracking is supported if you have the IOS based on the link below..
With your scenarios, it looks like your ISP hand of is Ethernet and based on the connection type, the gateway for the ASA may be directly connected router. So I suggest you track another IP (ex: ISP DNS server or any other reliable IP) for Internet auto failover. We have this tracking config in place at couple of our locations (3560SW) and works like champ..;-).