The minimum number of hops between this router and any
member of this IP multicast group reached via this next-hop
on this outgoing interface. Any IP multicast datagrams for
the group which have a TTL (IPv4) or Hop Count (IPv6) less
than this number of hops will not be forwarded to this
next-hop.
This is an optimization applied by multicast routing
protocols that explicitly track hop counts to downstream
listeners. Multicast protocols that are not aware of hop
counts to downstream listeners set this object to zero.