I am trying to run a game server and when using my router out side connections have been unable to connect. When I removed my router and directly connected my PC to the internet they were able to connect fine. This leaves me with the belief that it has to by my router.
I have my port forwarded and I am able to connect using my external IP when it is so. When I do not have it forwarded I am unable to connect using my external IP. It is strange to me that it seems to work correctly for me but for no one else ( I have 6 people from 6 different locations helping me to test).
I have also set my pc up as DMZ to see if the router's firewall may be the issue. Again I can connect fine from my external IP even without port forwarding if DMZ is enabled but no one else can.
I have been at this for 3 days now and would appreciate any help you could offer.
When you connect using your external IP are you on your network? If so, then that's why you can connect...technically, your connection is not leaving your network therefore not really testing the external IP connect attempt.
Your method of troubleshooting is spot on. With the information you've provided, we can determine that it is your router.
When forwarding the port in the router, are you ensuring both UDP and TCP are enabled for the connection.
Are you only forwarding 1 port? Sometimes there are alternate ports that need to forward as well.