The two next problems will be about an error message while connecting / DLCs maps, here is a little explanation before.
There are "two" 22.214.171.124 version on Tekno, a normal "126.96.36.199" and a "188.8.131.52-DLC maps", these two version aren't compatible.
You won't be abe to connect on a server with DLCs with a No-DLCs game and vice versa.
I advise you to make a copy of your MW3 folder and put the DLC maps in one of them.
Even if you tried DLC / No-DLC game and you have this message on a server, well, I don't know why does it display it, I also have error message on some servers.
"I got a message : "Files different from server"" : It means that you are playing with the 184.108.40.206-DLC version and you try to connect on a server which doesn't have DLCs MAPs on it. Update to a DLC version or make a copy for it (Like I advised you before).