Testing Port Forwarding from inside network?

[humbletech99]

I'm curious about something, I have a linux firewall using iptables and port forwarding. If I try to connect to the external port from inside the NAT, the port doesn't seem to be forwarded to the server on the inside network, which means I can't test the port forwarding.

Does anybody have any detailed insights into why this is or what I can do about it?

[gtmtnbiker98]

Never test firewall settings from inside the protected network. That is the common "rule of thumb."

[humbletech99]

but I want to know why this doesn't work....

Technically shouldn't the NATted connection go out as if it came from one of the router's dynamically allocated high ports, back to another port on the same router which is forwarded to the internal server , which replies back to the router, which passes it back to the NAT port which passes it to the internal host from which the tcp connection originated.

I want to create tests to make sure that the external port forwarding is working...