When using the "Computer Assignment Rules" under Settings -> Discovery & Assets -> Assets Management. You can set a rule for "If IP Address is like" "Assign to site". But the IP matching seems to be a simple *.*.*.* format. Which causes a lot of issues.
It should support CIDR based addresses like 10.9.36.0/23. So I don't have to enter two rules for 10.9.36.* and 10.9.37.*.
The current system fully breaks down when you make smaller subnets like a /25.