L4D2: Duplicate client connection ?
 

I opened my dedicated server, and use "mm_dedicated_force_servers [server IP]" to enter the server from lobby (for my friends to join more easily), it worked fine before, yet I can still use the cmd "connect [server IP]. But after the update, I got this error

**S3: Duplicate client connection: UserID: 3 SteamID 11000014a260575 RejectConnection: 192.168.1.1:27016 - STEAM validation rejected

I tried "sv_lan 1" to enter, yes I can enter, but I was like cloned (The status showed that I have already entered, so I appeared the clone of myself, like the bots with the same name "Nick, (1)Nick").

Any idea how to tackle this issue folks ? Thank you