Port Forwarding Troubleshooting
From DD-WRT Wiki
Introduction
This page explains how to troubleshoot common port forwarding troubles to figure out what the problem really is so that you can fix it. There can be many problems including multiple layers of NAT (router behind another router), misconfiguration of the port forward, software firewalls on the host being forwarded to, unexplainable behavior caused by not hard resetting the router, etc. You should first familiarize yourself with how to configure Port Forwarding before trying to troubleshoot it.
(more to come soon)