Linux/Routing

How can service D communicate with Service A?

[           HomeserverVM - 1           ]                 [                ServerVM - 2               ]
Docker:Service A   <-->   OpenVPN Client <-------------> Docker: OpenVPN Server <--> Docker: Service D
       >A<                    >B<                                      >C<                      >D<
   172.111.1.2             10.8.0.2                                172.1.4.3                 172.1.4.5

2) Server VM

ip route add 172.111.0.0/16 via 172.1.4.3 dev br-...openvpncontainer..

2-C)OpenVPN Server

iptables -t nat -A POSTROUTING -o tun0 -j MASQUERADE

server.conf:
route 172.111.0.0 255.255.0.0

clients/homeserver:
iroute 172.111.0.0 255.255.0.0