We currently have one main ISP circuit coming into our data center. It goes to a Catalyst 2950 which is the Internet switch and then to an ASA 5540 and a 6509 that does all layer 3 routing. A second ISP circuit has been installed for backup purposes and I am trying to decide how best to set it up. I have an additional ASA 5540 plus extra switches and routers that are not in use and can be used if needed. I want the internal network to stay the same, just with the ability to flip outbound traffic out the different gateway if needed and also would be setting up additional A records using the new ISP public IPs mapped to our internal servers such as the e-mail server and web server so that if the main circuit goes down, incoming traffic still transparently comes through via the second circuit.
Has anyone done, or is doing this sort of scenario?