The IP multicast group address which, when combined with
the corresponding value specified in
hwIpMcastRouteNextHopGroupPrefixLength, identifies the groups
for which this entry contains multicast forwarding
information.
This address object is only significant up to
hwIpMcastRouteNextHopGroupPrefixLength bits. The remainder of
the address bits are zero. This is especially important for
this index field, which is part of the index of this entry.
Any non-zero bits would signify an entirely different
entry.
For addresses of type ipv4z or ipv6z, the appended zone
index is significant even though it lies beyond the prefix
length. The use of these address types indicate that this
forwarding state applies only within the given zone. Zone
index zero is not valid in this table.