At work, I'm connecting to our VPN using a wireless router. Everything works great and I have no problems. At home, I can make an initial connection and ping our servers, connect via RDP and such.
However, after a minute or so, the connection dies. The info in the task bar still says that I'm connected but pinging the servers give me timeout. I've also noticed that when I'm on the VPN, the internet isn't available. I have to disconnect from the VPN (not that I seem to be on it) and then surf places. (The last part could be due the internet traffic being directed through VPN, though.)
We've got fiber here and the brand of the modem is Dlink DIR-645 (it's the round one), hardware version A1, firmware 1.01.
I'm almost certain it's my router and its settings that are to blame. Tested on two computers (Win7 and Win8). When connecting via 4G-modem, I have no problems either.
I've read about MTU but it's already set to maximum 1500 so that's not it, either.
What can I do about it?
What more can I investigate?