RADIUS attribute from rfc2865

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Login-IP-Host

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.0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |            Address
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            Address (cont)         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      14 for Login-IP-Host.

   Length

      6

   Address

      The Address field is four octets.  The value 0xFFFFFFFF indicates
      that the NAS SHOULD allow the user to select an address.  The
      value 0 indicates that the NAS SHOULD select a host to connect the
      user to.  Other values indicate the address the NAS SHOULD connect
      the user to.

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