When pushing a DNS resolver to an OpenVPN client, does the resolver see the IP address of the client or the OpenVPn server?

Question

When configuring an OpenVPN server, you have the option of pushing DNS resolvers to the client - like so:

push "dhcp-option DNS "

If this approach is used and a public DNS resolver is defined, will the DNS lookup be performed via the connected OpenVPN client, or by the server? In other words - will the DNS resolver see the real IP address of the client running the OpenVPN software, or will it see the IP of the OpenVPN server?

Answer 1

The DNS server will be access based on the routing table and thus the answer depends how the routing is setup and where the DNS server is. Usually: if the DNS server is in the same subnet as the OpenVPN then it will see the OpenVPN specific IP of the client. If the DNS server is outside and all traffic is routed through the VPN then it will see the public IP address of the tunnel endpoint.