We have a web application we developed, which we sell access to. We have eliminated all single points of failure from the firewall back to the application (firewall clusters, redundant switching, vmware cluster, sql cluster, load balanced web servers, etc). However, we only have a single 15mb fiber WAN link to our ISP. We are generally pretty small time, but have made some creative designs that got us this far.
However, I'd like to make the WAN link redundant for incoming traffic.
Our firewalls (SonicWall 2400's) support WAN redundancy, and will load balance outbound traffic.
How do I provide inbound redundancy for the web servers?
I can get a metro wireless (4G, 6mb down / 1mb up) connection for under $100/mo. I would want it only as a FAILOVER for incoming traffic. I don't want to load balance, unless I can direct MOST of the traffic to the fiber link.
I've read some about BGP, but it looks like it will be too "big" for me (requires at least a /24 IP range, and potentially some expensive hardware, etc). Can you do BGP cheaply/simply? Also, it seems BGP doesn't let you control which incoming route users will take, and I prefer they all go through the fiber link unless it's down.
Are there any DNS tricks, or anything else, I can set up that provide fail over? Even if it's not immediate, can we at least get something that will automatically switch over within a few minutes?
Aside from the ISP cost, I want to do something that's well south of $1,000.