As per RFC 2865:
This Attribute indicates the system with which to connect the user, when the Login-Service Attribute is included. It MAY be used in Access-Accept packets. It MAY be used in an Access-Request packet as a hint to the server that the NAS would prefer to use that host, but the server is not required to honor the hint.
A summary of the Login-IP-Host Attribute format is shown below. The fields are transmitted from left to right.