Thank you for your input.
Then I suspect there's something else that is not right.
I've noticed that you cannot set up a new RUT device with the startup wizard if you try to configure the LAN with a smaller subnet, say a /28 size. I always have to revert to a /24 to get the wizard to go through.
This configuration does not work for me, and I guess that I could get it to work with full class C /24 subnets;
If I use the auto-scan feature and pinpoint the specific device, it works.
Then the routes have a netmask of 255.255.255.255.