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Is there a good documentation for SonicOs 7.X on the TZ470 for the configuration of RDP for accessing office machines from a remote location?
I have not seen it in the Admin Guide.
RDP port Forwarding is not recommended as per security prospective. Instead to open the RDP port in public, you can use the SSL VPN / Global VPN client for accessing the office machines from remote location.
If you want to open RDP port in public, Follow the below KB;