IKeV2 VPN Tunnel for Windows Native Client and DHCP from internal Tunnel Interface - DHCP

Hello,

i have a working VPN Device Tunnel (named FG-VPN-Device) for my Windows 11 Clients. These clients can connect on a certificate based authentication with the fortigate firewall.

The Tunnel is configured with Mode Config enabled and a the IP is assigned with a Client IP Range (10.58.58.50-10.58.58.99).

But i can´t route any traffic over SD-WAN with this config, as the IP Range has no gateway.

After some more reading, i think, that i need to set a IP and DHCP Server for this Interface (named FG-VPN-Device).

I followed this article 

DHCP IP address reservation with Dial up ... - Fortinet Community

But after settings these options, the Windows 11 Client can´t connect anymore.

There is no DHPC assignment to the client.

any idea what is missing?