This document does not change the protocol or semantics of [RFC 6811
], BGP prefix origin validation. It highlights an important use case of origin validation in external BGP (eBGP) egress policies, explaining specifics of correct implementation in this context.
The term 'effective origin AS' as used in this document refers to the Route Origin Autonomous System Number (ASN) [RFC 6811
] of the UPDATE to be sent to neighboring BGP speakers.
The effective origin AS of a BGP UPDATE is decided by configuration and outbound policy of the BGP speaker. A validating BGP speaker MUST
apply Route Origin Validation policy semantics (see Section 2
of RFC 6811
and Section 4
of RFC 8481
) after applying any egress configuration and policy.
This effective origin AS of the announcement might be affected by removal of private ASes, confederation [RFC 5065
], migration [RFC 7705
], etc. Any AS_PATH modifications resulting in effective origin AS change MUST
be taken into account.
This document updates [RFC 6811
] by clarifying that implementations must use the effective origin AS to determine the Origin Validation state when applying egress policy.
The key words "MUST
", "MUST NOT
", "SHALL NOT
", "SHOULD NOT
", "NOT RECOMMENDED
", and "OPTIONAL
" in this document are to be interpreted as described in BCP 14 [RFC 2119
] [RFC 8174
] when, and only when, they appear in all capitals, as shown here.