Make lan behind OpenVPN client accessible from server (and its lan)

[mgiunktode]

Hello everybody,
I have two routers with Voxel firmware. One acts as a OpenVPN server while the other is a OpenVPN client which connects to the server (TUN). Here is the schema

CLIENT LAN <---> OpenVPN Client <---> OpenVPN Server <---> SERVER LAN

Hosts in CLIENT LAN can access hosts in SERVER LAN by using usual SERVER LAN IPs: as expected.

I also want that hosts in SERVER LAN can access hosts in CLIENT LAN but it doesn't seem to work. I get no reply to ping for example.
In fact I cannot see a route on OpenVPN Server which directs the traffic form SERVER LAN to CLIENT LAN.

I suspect the the is a form of masquerading which I would like to disable so that CLIENT LAN en SERVER LAN host can see each other directly.

Any hint or configuration files to accomplish this?

Thanks in advance