Setting this field to a 4 octets length value means that ip mapping (using rlSNMPv3IpAddrToIndexTable) is used for this row. If such a mapping is not used, a 0-length octet string value should be used for this field (this is also the default). This field value is determined only once, upon creation of an entry in the snmpTargetAddrTable. A change in its value while updating an existing entry is ignored. Prior to creating a snmpTargetAddrTable entry with a 4 octets length value for this field, the rlSNMPv3IpAddrToIndexTable must be used in order to retrieve this value.