Problems with VPN from site with same host IP address

[nphansen]

I have an RT-N66U setup as VPN server. The router has a gateway IP address of 192.169.1.1.

The VPN is working as expected. I can connect without problems both with PC and Android phone. I can access my routers web interface on 192.168.1.1 and any on my LAN devices on 192.168.1.x etc.

However, one day I was at a friends location. He happens to have a router (different type) with the same gateway address. This apparently gives some problems.

In normal working circumstances, when I'm connected through VPN to my home LAN, accessing 192.168.1.1 would give me my routers web interface. However, from my friends place, when I access 192.168.1.1 I get his router!

Is this normal behaviour? Or is something incorrectly configured?

I guess a quick fix would be to change the gateway address on my router. However, that potentially gives a problem somewhere else.

 

[YeOldeStonecat]

Normal.
VPNs need different subnets at different ends. Otherwise...how is the VPN supposed to know how to route traffic? Which side of the fence is 192.168.1.1 on? You see the confusion?

When we setup offices with VPN connections connecting them (like wide area networks)...offices are always on different IP ranges.

*Main office at 192.168.10.xxx
*Branch office A at 192.168.11.xxx
*Branch office B at 10.1.1.xxx

etc. We always try to setup offices at NON-common subnets...like, I don't set up my clients offices at 192.168.1.xxx or 192.168.0.xxx....because they may want to VPN in from home, and most home grade routers are in that IP range by default.