RADIUS Attribute - NAS Identifier

As per RFC 2865

This Attribute contains a string identifying the NAS originating the Access-Request. It is only used in Access-Request packets. Either NAS-IP-Address or NAS-Identifier MUST be present in an Access-Request packet. Note that NAS-Identifier MUST NOT be used to select the shared secret used to authenticate the request. The source IP address of the Access-Request packet MUST be used to select the shared secret.

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