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RFC 9929: IGP Unreachable Prefix Announcement

In plain English — editorial summary, not part of the RFC

Summarization is often used in multi-area or multi-domain networks to improve network efficiency and scalability. With summarization in place, there is a need to signal loss of reachability to an individual prefix covered by the summary. This enables fast convergence by steering traffic, when applicable, away from the node which owns the prefix and is no longer reachable. This document specifies protocol mechanisms in IS-IS and OSPF, together with two new flags, to advertise such prefix reachability loss. The term "OSPF" in this document is used to refer to both OSPFv2 and OSPFv3.

Document record

Document ID
RFC9929
Published
February 2026
Authors
P. Psenak; C. Filsfils; D. Voyer; S. Hegde; G. Mishra
Status
PROPOSED STANDARD
Stream
IETF
Area
rtg
Pages
14
Also known as
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The document record above — title, authors, date, status, stream, area, relationships, DOI and errata — is imported verbatim from the public RFC Editor index. The “in plain English” section is editorial: written by The metasystema editorial team, not part of the RFC. Where the two differ, the RFC text governs.

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canonical URL: /rfc/9929-igp-unreachable-prefix-announcement