No worries spartacus, in the meantime I am simply sparring with mkx over some minutia.
So mkx,
The questions comes down to what is most efficient.
a. asking the CPU to inspect the forwarded packet for IP, protocol and port (and discarding those that do not fit) OR
b. asking the CPu to inspect the forwarded packet for IP only (and discarding those that do not fit).
The questions I have is why would anyone on the originating LAN be hitting that IP address with anything other than the right protocol and port?
Does the admin expect some folks on the originating LAN to try and hit the server with different types of traffic (hack in?) ?
c. What is more efficient wrt to CPU load?
To have a rule that inspects a packet for allowable IP (which it does) but it has wrong port or protocol and drops it?
VERSUS
The packet is passed to the server (allowable IP) but the packets hits a closed port, or even an open port but with the wrong protocol.
I believe the latter events are transparent to the CPU (no load).