Connection through VPN and another subnet

Question

I'm a Java Developer and for a few weeks I'll be in charge of the network as well. A client of ours wants a VPN connection to his network which I already mounted (Using a TP-link router to stablish the IPSEC Tunnel LAN-to-LAN).

Our network: 110.110.1.0/24

Client's network: 192.168.100.0/24

But to my surprise the connection purpose is to be able to connect to a specific Server wich is in a different subnet.

Client's Server: 192.168.1.68/32

So it's in a different subnet (different netmask ofc)... How can I achieve the connection? I know that the netmask doesn't mean anything in a LAN-to-LAN connection but since the target is in a different subnet with a different netmask.

In my opinion (I'm not an expert) we should just do the VPN to the subnet where the server is.

Answer 1

VPN Tunnels are to be implemented between the Border routers. And usually use the external interfaces. The IP addresses you shared are private IPs, this shouldn't work. You need public IPs for the tunnel.

To connect to the server you can use a GRE Tunnel that will pass through the vpn and will go directly to the server.

In uni at least that was the way to connect between two remote subnets.

Update: I have done a small research on the matter, and found that VPN tunnels are used such as to connect two remote sites like there were connected with a single cable, so it doesn't matter how many subnets there are in the network.

There are different tunnel types, and some cannot carry broadcast/multicast traffic, so some routing protocols or multicast routing may not work over that tunnel type. You could use a GRE tunnel inside that type of tunnel to overcome this, or use a different tunnel type that supports the features you need to support. Another possibility is to use static routes between the sites, but that doesn't scale, and it is not dynamic the way routing protocols are.