Remove default route or increase its metric from DHCP server

[ekravchenko]

My setup is one FortiGate 80F with latest firmware (7.4.1) and lots of services and hosts behind it. I have multiple VLANs that i use for VPN clients. VPN server is separate host and it assigns VLAN to the client. FG acts as DHCP server for VPN clients. Also i use DHCP option 121 to push routes to internal resources depending on VLAN. What i want to achieve is to remove default route from DHCP server or make its metric higher so vpn clients will have only option 121 pushed routes.
Now i`m using blackhole route but it doesn`t fullfill my requirements as i still have clients with problems. I use softether as VPN server and clients are windows, linux, mac users using softether protocol and openvpn protocol.
Any ideas?

[AEK · Accepted solution]

If I understand well your concern, a solution would be to configure FG as DHCP relay, and IP assignment will be done by VPN server.

[ekravchenko]

I think i will proceed with VPN server DHCP server. Thank you

[spoojary]

Absolutely, making the FortiGate (FG) act as a DHCP relay agent and letting the VPN server handle the IP assignment directly can provide greater control over the DHCP options distributed to clients. By doing so, you can configure DHCP options, including Option 121, precisely as desired on the VPN server without the FortiGate potentially introducing any unwanted options.