A strange one for me: Just changed out old router for OpenWRT at mom's house (network 1). While on the OpenWRT network (network 1), when I try to OpenVPN out to my home machines (vpn runs on PFSense; network 2) I can connect, my IP changes to my home IP, but I can't access any 'local' machines (read: machines on nework 2). When I access 192.168.1.1 I get the OpenWRT admin panel not the foreign PFSense one I am expect if my OpenVPN connection were tunnling everything. When I connect via my mobile hotspot everything works fine. It was also working fine with previous non-OpenWRT router (though only was using windows NFS access via my wifles computer). This happens if I use IP or hostname of the 'local' machines (on network 2)
Any idea why/how OpenWRT is intercepting what I would think is a full VPN tunnel and taking all requests for local machines for itself?
OpenVPN (tun) is a routed solution so it needs three different subnets.
The subnet of the OpenVPN server, the subnet of the OpenVPN client and the OpenVPN subnet all need to be different.
Maybe the server and the client both have 192.168.1.0/24?
So to be clear, because I'm not quire sure I understand: I don't have any OpenVPN installed in OpenWRT. The VPN I'm trying to use is all a foreign setup from my home (PFSense VPN server). I would expect to just pull up an openvpn client and connect to my home without messing with OpenWRT at all (since the client is supposed to make a point-to-point connect with that home server. My expectation is correct with both the stock router and my mobile network hotspot: 1) launch OpenVPN, 2) connect 3) ssh/rdp/etc into 'local' machines (no messing with networ). This workflow almost everywhere: old router, mobile network, airports, schools, friends home, coffee shops etc. The only place it doesn't seem to work is my new install OpenWRT at my mom's house. I'm not sure what non-VPN settings I need set (I DO NOT want VPN setup on OpenWRT, I just want to be able to use a VPN CLIENT on this OpenWRT network.)
Unless you're saying I have to setup an OpenVPN SERVER on OpenWRT even though I just want to use the OpenVPN CLIENT. That seems strange to me that I would have to do that as none of the other solutions seem to need that type of setup.
As @egc said, the LANs in the two houses need to be different IP ranges for it to work. Otherwise the routing table in the laptop or phone will send 192.168.1.1 to the local LAN instead of down the VPN tunnel. Since a lot of hotels etc may use 192.168.1.0, it's a good practice to use an obscure IP range at the house that you are VPNing to.