I've tried searching, but nothing seems to be working. I have a feeling it might be due to our custom Rewrite module. Here is the excerpt from the web.config that sets it up:

<modules runAllManagedModulesForAllRequests="true">
  <add name="UrlRewriteModule" type="EShop.UrlRewriteModule"/>
</modules>

EShop.UrlRewriteModule is a custom class in App_Code which handles incoming requests. I have set up the rewrite rules but it doesn't seem to want to work. I'm inclined to think that our rewrite class is interfering earlier than the proxy rules and saying that the page doesn't exist.

Here's what we're trying to accomplish: We are working on a new site for a client, but they have a forum that they're not likely to want to move. I set up a new subdomain to point to the new server while the site is being completed (before we go live) and want the reverse proxy to forward test.domain.com/forum to www.domain.com/forum. After the site goes live, we'll need to forward using an IP address instead.

I've set up a reverse proxy successfully with nginx, but we didn't want to set up another server if we didn't need to.

Ideas?