How to Port Forward for "Garry's Mod"
Garry's Mod is a free online game where you have unlimited access to use the tools you're given to carry out actions, such as creating images, posing with available tools or taking screenshots of the creations. You can even use physics to make vehicles or functional roller coasters. Your friends can interact with you through the game by walking through your creations similar to sightseeing. If you cannot connect to others due to blocked ports, you need to use a program to port forward Garry's Mod.
Log in to your router using its Internet protocol (IP) address, which varies based on the manufacturer. Linksys access is "192.168.1.1" with the default username blank and password of "admin." NetGear uses "admin" for the username and either "password" or "1234" by default.
Click the "Advanced" tab, then select "Port Forwarding." It may also be located under "Applications and Gaming."
Type the name of the application, "Garry's Mod," into the application.
Enter "27005" for the Start and "27015" for the End range.
Select "Both" from the protocol drop-down menu. Check the box next to "Enable" to turn it on.