Ive been a lurker for some time , quite a lot in the past few days in trying to diagnose my problem.

Let me give you the history

4 or so days ago my network slowed down ( i was running rh9 at the time).
I use cable-modem > firewall > local net
Normally have a few ports forwarded to my machine on the local net.

But when it slowed down i re-installed .. did everything from scratch , including replacing all my network cards.

I just diagnosed the problem however.

The problem is - if i forward ports to my machine using dnat my connection to the net ends up about 300-1600ms
However if the ports are not forwarded - the connection returns to "normal".

Ports being forwarded 4662-4667 tcp & 4665 udp.
Why would this slow the network down.

Oh btw i am now running mandrake 10.

Any theorys welcome