InetZoneIndex
A zone index identifies an instance of a zone of a specific scope. The zone index MUST disambiguate identical address values. For link-local addresses, the zone index will typically be the interface index (ifIndex as defined in the IF-MIB) of the interface on which the address is configured. The zone index may contain the special value 0, which refers to the default zone. The default zone may be used in cases where the valid zone index is not known (e.g., when a management application has to write a link-local IPv6 address without knowing the interface index value). The default zone SHOULD NOT be used as an easy way out in cases where the zone index for a non-global IPv6 address is known.