OpenVPN server with one network card?

Question

linux

Hello Lord!
There is a network divided into a bunch of VLANs 10.0.0.0/8
There is a certain server on Debian, inside the local network 10.1.2.250
UDP port 1194 was forwarded through the gateway from the Internet to this server.
Is it possible to configure OpenVPN so that a user from the Internet can see the local network through it?
I understand that the way of the curve is impossible, but so far there is no other choice. The server is located on the local network and is accessible from the Internet only via UDP 1194.
What has already happened:
1. external users connect to OpenVPN
2. These users can climb the server
3. Users can ping IP 10.1.2.250 (server IP in the local network)
Unfortunately, that's where the success ended. I can't ping any more IP from the local network.

Answer 1

Apparently, packet forwarding is not enabled on the server (net.ipv4.ip_forward) or the firewall is not configured (both options are possible). Google any guide for setting up openvpn, among other things it says about it.
And do not forget about routes in both directions, of course, as you have already been advised.