Wireguard not routing traffic from client to other servers on the network

After so many try and fail and brainstorming with wireguard IRC chanel guys, apparently I forgot to add a static route for for each server behind wireguard. Ping goes to the server, but does not return as server does not know where to send that echo-reply:

ip route add via dev eth0 (main device for communication)

For me, problem solved ;-)

I ran into the same problem - my server aka "Wireguard SRV" in rhe diagram (=Centos8, with iptables and ferm) doesn't route traffic.

The problem: I forgot to sysctl -w net.ipv4.ip_forward=1.
But that was not the only issue - ip route add ... was not the solution.

So I added these lines to my wireguard-config (located at /etc/wireguard/wg0.conf according to your addresses):

// ...
PreUp = iptables -A POSTROUTING -s -o eth0 -j SNAT --to-source -t nat
PreDown = iptables -D POSTROUTING -s -o eth0 -j SNAT --to-source -t nat