Internet access through VPN on Ubuntu server

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http://serverfault.com – I'm trying to set up a VPN server on ubuntu which provides internet. I used an article that describes how to do it http://toolongdidntread.com/linux/setting-up-a-vpn-server-on-ubuntu-to-a... but once I connect via VPN the only address which is working is google.com. It looks wierd. It takes forever to load any other interet resource. Once I uncheck use VPN connection as a default gateway in the VPN connection settings, I can use internet My knowledge of *nix based systems is very poor, so I even can't find a way to troubleshoot the problem (HowTos)