Expand the scope of the VPN
Suppose a client machine connects to the VPN and at the same time to the local LAN. In this case such client can act as a gateway for the LAN and VPN clients will be able to reach LAN machines through it. Next image illustrates the situation.
To achieve connectivity between VPN and LAN clients following adjustments are needed.
OpenVPN server
Tell the OpenVPN server that the 192.168.178.0/24 subnet should be routed to a LAN gateway. For this the LAN gateway configuration should contain (can be set through the ccd directory):
iroute 192.168.178.0 255.255.255.0
Then set in the main server configuration file:
route 192.168.178.0 255.255.255.0
Also, to allow network traffic between LAN and VPN clients ask OpenVPN server to advertise LAN subnet to VPN clients by adding to the server configuration:
client-to-client
push "route 192.168.178.0 255.255.255.0"
LAN gateway
Enable IP forwarding (to make it persistent add “net.ipv4.ip_forward=1” to the /etc/sysctl.conf):
# sysctl -w net.ipv4.ip_forward=1
Set the iptables rule (iptables-persistent package can be used to make it persistent):
# iptables -t nat -A POSTROUTING -j MASQUERADE
References