I have been working on a NAT 1:1. I have been able to make it work but I still have an issue that the application that is behind the NAT, a PRTG, response too slow, even sometimes I get an error of time out.

So far this is what I done. My firewall rules are set to any source, destination and port in both interfaces. Also in the NAT 1:1 rule I set the reflection option to enable. The rules for the NAT Outbound are disable. Also I don't configure any static route. The VIP that I create I set the type to Proxy ARP.

Could anyone give me some advice?

By the way my server is a virtual machine in Citrix XenServer.

Thank you very much for your help.