We have a single IIS web server in house that when it goes down we would like to redirect traffic to another web server and display a message that the web site is down. I have been all over the net but I cannot find quite what I need. This is a single web server setup so I do not have a load balancer. All dns and routers are in house.
I think the answer is in your question: Get a Load Balancer/Reverse-Proxy! (-:
Two that come to mind are:
Varnish can be installed on the same server as IIS, set to listen to port 80. Then define the web server to listen on another port, say, 8080, and set up a
Varnish is usually used for caching, but you can turn that off. OR. You can store pages in varnish cache even if your backend is down and present them to your users which you fix the backend. Look at Varnish's grace and saint modes. Check out the docs at the above links. If you are not familiar with these products, there is a bit of a learning curve, IMO.
HTH, and good luck!