RADIUS Attribute - NAS Port

As per RFC 2865

This Attribute indicates the physical port number of the NAS which is authenticating the user. It is only used in Access-Request packets. Note that this is using "port" in its sense of a physical connection on the NAS, not in the sense of a TCP or UDP port number. Either NAS-Port or NAS-Port-Type (61) or both SHOULD be present in an Access-Request packet, if the NAS differentiates among its ports.

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