OpenVPN client in DMZ cannot access LAN

[corale]

My OpenVPN client is installed on a Windows Server 2008R2 located in the DMZ.

When the OpenVPN client is disconnected I can access a database server located on the LAN.
Once I connect the client (to an ExpressVPN server) I cannot reach the database anymore.
Again, after disconnecting the VPN client everything comes back to normal and I can reconnect to the database.

I've improvised without success around several scenarios dealing with similar routing issues.

Can someone please help me in finalizing this setup?

Map:
VPN Server: 64.20.51.36

DMZ: VPN Client: 204.204.204.24 Gateway: 204.204.204.33 DNS Server: 172.28.14.30

LAN: Target : 172.28.23.20 Gateway: 172.28.23.1 DNS Server: 172.28.14.30


OpenVPN version: 2.4.9 x86_64-w64-mingw32 [SSL (OpenSSL)] [LZO] [LZ4] [PKCS11] [AEAD] built on Apr 16 2020.

Thank you,
corale

[TinCanTech]

You cannot do what you are trying to do with Windows.