This read-only OCTET STRING is a bitmap where each bit position represents a parent group address ID, with the most significant bit corresponding to group address ID 1, and the description notes this object only applies to a local individual address, showing which SMDS groups this individual address is a member of. This lets an admin see group membership from the individual address's perspective without needing to check every group's own member bitmap individually. An engineer verifying that a customer's SMDS address correctly receives multicast traffic for group ID 3 would check that bit position 3 in smdsaddrParentGrpMap is set.