I have been out of networking for a few years now and attempting to setup a VPN. I have purchased two Draytek Vigor 2830 routers. The VPN is setup and works a treat however I have a routing problem access the network from the remote site.
You can NOT use the same network on both sites! That's not a suggestion, it’s a requirement!
The internet and TCP/IP depends on every computer having a unique IP address. Having the same IP scheme accessible from two different networks is like having two places in the country w/ the same physical address. So where should the postal service deliver your mail? You can't do it, not if you want it to work correctly.
The only reason each of us at our home networks are able to use the same networks (e.g., 192.168.1.x) is because normally they can't see/access each other. We're separated from each other by the greater internet, so it doesn't matter if I use 192.168.1.x in Los Angeles, and you use 192.168.1.x in London. But it matters a lot if we subsequently attempt to join those networks over a VPN. Now we have a conflict; two routers claiming the same addressing space. No can do. One of you MUST change!
Yeah, I know it sucks and can be problematic, esp. if you don’t control the network addressing scheme, but that’s just a requirement of getting the VPN to work correctly.