Hi there,
Yes, it is possible to use a single Radius Server 2019 for multi-site.
Some organizations and ISPs can use a central RADIUS service for all of their RADIUS needs. This configuration is possible when there are a small number of users, or the system load is low. However, when there are a large number of users spread across a wide geographic region, it may be beneficial to use a multi-site approach.
Here is a link for a detailed description of the process that you must follow. Plan NPS as a RADIUS server https://learn.microsoft.com/en-us/windows-server/networking/technologies/nps/nps-plan-server
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