The IP multicast group address which, when combined
with hwPimBsrElectedBsrGrpMappingGrpAddr, gives the
group prefix for this mapping. The InetAddressType is
given by the hwPimBsrElectedBsrGrpMappingAddrType object.
This address object is only significant up to
hwPimBsrElectedBsrGrpMappingGrpAddr bits. The
remainder of the address bits are zero. This is
especially important for this field, which is part of
the index of this entry. Any non-zero bits would
signify an entirely different entry.