Comment 1 for bug 1541490

I'm looking to this on Newton and I see similar issue. I don't se such traces but problem remains the same: subnet without a gateway cannot be used with dhcp.

Looks like it is by design:

def use_gateway_ips(self):
    ...
    return True

But you can use host-route of subnet if it suits your needs.

I suppose, support for subnet without gateway can be implemented but it's not just about changing of use_gateway_ips to False.