MIB: IF-MIB
The number of packets, delivered by this sub-layer to a
higher (sub-)layer, which were addressed to a multicast
address at this sub-layer.  For a MAC layer protocol, this
includes both Group and Functional addresses.  This object
is a 64-bit version of ifInMulticastPkts.

Discontinuities in the value of this counter can occur at
re-initialization of the management system, and at other
times as indicated by the value of ifCounterDiscontinuityTime.