NimbostratusThe way Npath is meant to work is that the LB would not translate the client address or port when sending it to the server and the server needs to listen to the same IP as the VIP does. It's a bit counter intuitive and I only had the pleasure of setting it up once.
From way you describe it the only solution I can think of if looking at the situation as is is to use Npath. When reaching the whiteboard you might want to check out this article. It's a bit old but it describes how it works.
But, the absolute best thing you can do is to move the application to a network behind the F5. You can still access the server directly via virtual forwarding servers if you do so.
/Patrik
