The time remaining until the local router will assume that
there are no longer any MGMD version 1 members on the IP
subnet attached to this interface. This entry only applies
to IGMPv1 hosts, and is not implemented for MLD. Upon
hearing any MGMDv1 Membership Report (IGMPv1 only), this
value is reset to the group membership timer. While this
time remaining is non-zero, the local router ignores any
MGMDv2 Leave messages (IGMPv2 only) for this group that it
receives on this interface.