For origin validation we have a special case involving as0 and this is described in RFC 6480. It's known as disavowal of routing origination es0 has been reserved for network operators and other entities to identify non-routed networks and this means a raw with our subject of as0 is an attestation by the holder of a prefix that the prefix described in the raw and any more specific should not be used in a routing context any prefixes with a row indicating a 0 as the origin as need to be dropped if these prefixes appear with any other origin the rows will be invalid achieving this goal so where would we use it well es0 raw could be used for internal use of a prefix that should not appear in the global bgp table it could be used by internet exchange points because internet exchange point lan must never appear in the global bgp table either it will be visible in the member's routing table but would never appear visible on the global default free zone private address space perhaps for ipv4 and non-global unicast address space for ipv6 other possibility could be unassigned address space and at the time of this recording this was under active discussion in the various regional internet registry policy forum ipv4 and ipv6 address resources which should not appear in the global bgp table could also be signed with the as0 raw for example the special use address space described in RFC 6890.

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