Odd game server problem
 

Running a day of defeat game server for a client and having a funny issue. There is a handful of players that can't see or connect to their server through steam on port 27015, funny thing is they can ping it with a cmd line so it's not on their end. After looking at these people the only common issue is their IP address all start with the same first 2 digits as the server.What's even more strange is the same people can connect to the dod source server running on the same IP but on port 27016?? Does anyone know what might be causing this issue I have looked everywhere but can't find an answer for it. I ran a ping back to the client and get 100% loss, and traceroute drops after a few hops. The server is pretty much open and it's running on FC4. Any ideas would be appreciated.

You sure your web provider doesn't have an argument with the provider of the gamers? Stupid idea, but that happens in my country, and those from one provider can't connect to the computers of the other provider...

As far as I know, and from having the people talk with their ISP's there are no issues between them.

Ok, a few more suggestions:
1. Make sure the firewall isn't blocking that IP range on that port. Check the log files.
2. The lost packets in ping and dropping traceroute sounds familiar to me... Maybe they are behind a server that blocks ping packets for security reasons (and if ping doesn't work, traceroute doesn't work) and maybe it also doesn't allow users to connect to that specific port.
The only solution I see is to change the default port, if you say it works on a diffrent port for them.