RFC 9929 on IGP Unreachable Prefix Announcement

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        RFC 9929

        Title:      IGP Unreachable Prefix Announcement 
        Author:     P. Psenak, Ed.,
                    C. Filsfils,
                    D. Voyer,
                    S. Hegde,
                    G. Mishra
        Status:     Standards Track
        Stream:     IETF
        Date:       February 2026
        Mailbox:    ppsenak@cisco.com,
                    cfilsfil@cisco.com,
                    davoyer@cisco.com,
                    shraddha.hegde@hpe.com,
                    hayabusagsm@gmail.com
        Pages:      14
        Updates/Obsoletes/SeeAlso:   None

        I-D Tag:    draft-ietf-lsr-igp-ureach-prefix-announce-11.txt

        URL:        https://www.rfc-editor.org/info/rfc9929

        DOI:        10.17487/RFC9929

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.

This document is a product of the Link State Routing Working Group of the IETF.

This is now a Proposed Standard.

STANDARDS TRACK: This document specifies an Internet Standards Track
protocol for the Internet community, and requests discussion and suggestions
for improvements.  Please refer to the current edition of the Official
Internet Protocol Standards (https://www.rfc-editor.org/standards) for the 
standardization state and status of this protocol.  Distribution of this 
memo is unlimited.

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