Port changes on server restart

[darkjuggle]

Ive been having a weird problem since i started my source server. Yesterday when i started it the ip for it was something like: 99.225.198.81:27015. After a few server restarts the port started changing. The 27015 started to change to different numbers and wouldnt appear on the server list, only if you added the ip. After a while it showed up but the port always changes. I tried to forward my ports for steam but that did not do anything. If anyone knows how to stop the ports from changing pelase help me out. Also my router is a d link 624.

Thanks