bad gateway problem

I'm fairly new to configuring F5 devices, so feel free to tell me if there is a better forum to post this to. I am using the virtual edition on Virtual Box to test this. Version BIG-IP 10.1.0 Build 3341.1084 Final.

 

I'm attempting to use the F5's we are about to use to load ballancer https traffic to alter outgoing requests to use differnt snat output interfaces based on HTTP headers. That side of it (using an iRule) was very easy to get going.

 

However I'm now doing a more production like test (rather than proof of concept) and I'm having a little trouble with the F5. F5 Config is really just 2 virtual servers. One incoming HTTP, and one outgoing any ip any port rule to map the internal connections to the external network. Other than that its a pretty blank F5 device (default gateways, IP's, Vlan config is set though).

 

My test scenario is:

 

* Customer web browser is outside the F5

 

* Request goes through F5 (to single server for ease now)

 

* Request goes into IIS through some ARR rules

 

* Request is initiated out from IIS to a site outside the F5 device

 

Also:

 

* When I bypass the F5 (bridge the server onto the external networ), the IIS request is initated out to the external site fine and response recieved by the client browser. So IIS is doing it's job correctly.

 

* When I make a request from the server (browser) out through the F5 to the external site, the F5 forwards it correctly to the external site, and the response is recieved correctly.

 

However when I join those two togeather for the full stack (in through F5 or not to the internal server, through IIS routing, and out from IIS through the F5, to the external site) I receive a 502.3 bad gateway response from the F5 device (it seems).

 

The external site never sees the request, and the internal IIS logs show it recieving a 502.3. "The connection with the server was terminated abnormally".

 

Any thoughts on what is going wrong, or how to debug it from the F5?