Not forwarding back packets through NAT firewall

[johnpoz]

Agree with KOM on that for sure.. If your sniffing on the actual server and you see a syn and no syn,ack back then that has nothing to do with anything other than that server.  Be it a firewall that never let the syn get to the application, or application not even running or listening on that port the syn went to.  Or it sent it out a different interface, or firewall blocking the outbound traffic from that application, etc.

But for sure its the box.. unless for some reason that syn was so malformed that was not answered.  Which seems very far fetched.