Server IP adress not working

[SCostilla]

I have a Team Fortress 2 SRCDS server that has not been able to have anyone join who is outside of our LAN. When I leave the server, the IP adress drops till it reaches 00.00.00.000. I have tried everything that my friend has helped me with, but we're both at the end of our ropes here. Can anyone help! The info is as follows: Windows 7 64-bit, Intel® Core™ i3-2310M Processor (3M Cache, 2.10 GHz), 3GB RAM, Team Fortress 2, startup command is C:\SRCDS\orangebox\srcds.exe -console -game tf -hostport 27015 +maxplayers 32 +map ctf_turbine, it runs sourcemod 1.3.8, has a ping of 46ms, a download speed of 10.90 Mbps, an upload speed of 1.46 Mbps, its router is 2wire 3801 HGV-B, local ip is 192.168.1.76, and its external ip is 99.28.93.107.

[Branti]

Open port in router. And use -ip and local ip in your startupcommand