OARC maintains a database of IP address space that should not be probed with DNS messages. An address or network may be listed in the database because it is known to be "dark" (such as RFC 1918 space, or certain large blocks held by the U.S. Department of Defense), or due to an abuse complaint where someone specifically requests no further probing of their network. The primary table contains six fields:
CategoriesThe following categories are currently defined:
cid | category -----+---------------------- 0 | Unknown 1 | User/admin complaint 2 | RFC 1918 3 | Bogon 4 | Military/Government 5 | Hoarder 6 | Exchange Point 7 | AcademiaIn order to be assigned the complaint category, the entry must have been made in response to an abuse complaint or specific request from someone responsible for the corresponding address space. Hoarder refers to early recipients of large address space blocks that are known to be unreachable from the public Internet.