Not sure about NPS but for Cisco ISE, one caveat with just adding the entire Management network in is that then using the Live Log for troubleshooting you will only see the NAD as the subnet, and not the device itself, as the NAD is created on the configured IP address. So if you need to determine which device it authenticating, you'll need to have added the NAD with it's host address, and not the entire network.
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