Advertising Unreachable Links in OSPF

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Publisher: IETF
Doc Type: Standard
Pages: 22
Abstract: OSPF Router Link State Advertisements (LSAs) use fixed-format encodings that always include advertised links in the default Shortest Path First (SPF) computation. For non-default SPF computations, e.g., Flexible Algorithms as described in RFC 9350, advertised OSPF links are used in the default SPF computation even if this is not intended. In order to advertise these links and not use them in the base SPF calculation, the metric LSLinkInfinity (0xffff) is used to specify that the link is unreachable. If all OSPF routers in an OSPF area support this functionality and have advertised the capability via an area-scoped OSPF Router Information LSA, then links advertised with a metric of LSLinkInfinity are considered unreachable. MaxReachableLinkMetric (0xfffe) is defined to provide backward compatible reachability in specifications that previously specified advertisement of MaxLinkMetric (0xffff). This document updates RFC 5443, RFC 6987, RFC 8379, and RFC 8770 with respect to the advertisement of MaxReachableLinkMetric (0xfffe) rather than MaxLinkMetric (0xffff).
Publication Date: 2026-09-01
Status Note: Proposed Standard
DOI: 10.17487/RFC10041
Link: https://doi.org/10.17487/RFC10041
Author(s): Liyan Gong
Weiqiang Cheng
Changwang Lin
Acee Lindem
Ran Chen
Keyword(s): LSR, OSPF

Latest version of IETF RFC 10041

Document Versions — IETF RFC 10041

▶ IETF RFC 10041 (2026-09-01)

THIS DOC [ACTIVE] [LATEST VERSION]

Normative Reference(s)

IANA, "OSPF Router Functional Capability Bits", <https://www.iana.org/assignments/ospf-parameters>. EXTERNAL
IANA, "YANG Module Names", <https://www.iana.org/assignments/yang-parameters>. EXTERNAL
IETF RFC 2119 [Active*]
IETF RFC 2328 [Active*]
IETF RFC 3688 [Active*]
IETF RFC 4915 [Active*]
IETF RFC 5340 [Active*]
IETF RFC 5443 [Active*]
IETF RFC 6020 [Active*]
IETF RFC 6987 [Active*]
IETF RFC 7770 [Active*]
IETF RFC 7950 [Active, Amended*]
IETF RFC 8174 [Active*]
IETF RFC 8341 [Active*]
IETF RFC 8349 [Active*]
IETF RFC 8362 [Active*]
RFC8379 — RFC8379 EXTERNAL
RFC8405 — RFC8405 EXTERNAL
IETF RFC 8770 [Active*]
RFC9129 — RFC9129 EXTERNAL
RFC9350 — RFC9350 EXTERNAL

Bibliographic Reference(s)

IETF RFC 4252 [Active*]
IETF RFC 6241 [Active*]
RFC7308 — RFC7308 EXTERNAL
IETF RFC 8040 [Active*]
IETF RFC 8340 [Active*]
IETF RFC 9000 [Active*]
IETF RFC 9846 [Active*]

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Full registry record with provenance metadata. Open directly: /api/doc/RFC10041.json

Amends:

IETF RFC 5443 [Active*]

IETF RFC 6987 [Active*]

RFC8379 — RFC8379 EXTERNAL

IETF RFC 8770 [Active*]

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IETF RFC 10041, Advertising Unreachable Links in OSPF
doi: 10.17487/RFC10041
url: https://doi.org/10.17487/RFC10041

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<cite id="bib-rfc10041">IETF RFC 10041</cite>, Advertising Unreachable Links in OSPF
<span class="doi">10.17487/RFC10041</span>
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