A while back I was trying to connect to a VPN. The setup worked well for other users, and worked well in other networks other than at home. However, at home, I would connect, and experience a brief period of connectivity of a few seconds at most. The connection would remain but all the requests would basically fail after that.
After a bit of searching I found that I needed to change the MTU setting on my router/modem. I browsed to the router administrative interface, then to Advanced Setup, then to WAN, and for each listing there I clicked Edit and updated MTU size from 1452 to 1492, clicked Next 3 times, and then clicked Apply/Save. It worked! I figured it out due to this fine forum.