Put Forward your ports,
http://www.portforward.com/ (Mentioned in Droconas Post)
and here are the ports,
[UDP] 1200 (used for Steam's Friends service)
[UDP] 27000 to 27015 (so that means all ports in between too)
[TCP] 27030 to 27039 (idem)
=> these are all Steam related ports
[UDP] 27015 and 27020 (default DS port, also used for HLTV)
[TCP] 27015 (you want to forward this for RCON access)
=> these ports are used by the dedicated server itself
http://www.portforward.com/ (Mentioned in Droconas Post)
and here are the ports,
[UDP] 1200 (used for Steam's Friends service)
[UDP] 27000 to 27015 (so that means all ports in between too)
[TCP] 27030 to 27039 (idem)
=> these are all Steam related ports
[UDP] 27015 and 27020 (default DS port, also used for HLTV)
[TCP] 27015 (you want to forward this for RCON access)
=> these ports are used by the dedicated server itself