I have two T1 lines from different providers and the requirement is to have the end-users default route be the one ISP and the servers default route the other ISP. Additionally, there needs to be a way for automatic failover should one of the lines fail. The final challenge is that all the traffic is coming from a 5510 ASA. The switches on the inside of the ASA are unmanaged but the servers connect to one switch and the workstations another so I can physically separate them and configure an interface on the ASA for each group.
I know it is a relatively simple task if all traffic goes out one line and the other is strictly failover. The crux of a solution like this would be a tracked default route, multiple route-maps, and multiple NAT statements. However, for the requirements mentioned above I am thinking of using route-maps setting the next hop of the preferred path and then the secondary path. The servers with static mappings are just hosed unless someone manually configures them with the secondary ISPs IP addresses or have an alternate config ready. I am never thrilled with a solution that requires manual input but it may be the chosen path. I would set IP precendence (or some other QoS marking scheme) for the workstation traffic to be able to distinguish it from server traffic and thus determine what route it takes.
I think all in all BGP would be the best bet provided I can get a /24 from one of the providers and both support BGP. However, just in case I am lining up other non-BGP alternatives.
Open to all thoughts and ideas. Thank you.