Sure. Normally when you use a router, you tell your computer to automatically get an IP address, which it does from the router. The problem is that I've seen the address the router assigns get changed for whatever reason. So, let's say you set up the ports to go to 192.168.1.100, and then your IP gets changed to 192.168.1.101. The ports are no longer reaching your computer because the IP address has changed.
So what you do is manually set your IP address in the Network control panel instead of letting the router assign it. That way the IP address doesn't change and your forwards don't get lost. Most routers will require a manually set IP address to be between 192.168.1.1 and 192.168.1.99. The manual of the router should tell you how to set it up.