Did you try to add a static route to the sonicwall to route the VPN network to the Nethserver?
This way the Sonicwall knows about the VPN and sends the packages to the NethServer and it should work without changing gateway settings on clients.
Did you try to add a static route to the sonicwall to route the VPN network to the Nethserver?
This way the Sonicwall knows about the VPN and sends the packages to the NethServer and it should work without changing gateway settings on clients.