The number of multicast packets that have been sent on the
interface. In many cases, this object is identical to
ifOutMulticastPkts in the Interfaces MIB.
However, some implementations use ifXTable for Layer 2
traffic statistics and hwIpMcastInterfaceTable at Layer 3. In
this case a difference between these objects probably
indicates that some Layer 3 multicast packets are being
transmitted as unicast at Layer 2.
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
hwIpMcastInterfaceDiscontinuityTime.