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Use of /127 Prefix Length Between Routers Considered Harmful

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 3627.
Author Pekka Savola
Last updated 2020-01-21 (Latest revision 2002-06-28)
RFC stream Independent Submission
Intended RFC status Informational
Stream ISE state (None)
Consensus boilerplate Unknown
Document shepherd (None)
IESG IESG state Became RFC 3627 (Historic)
Action Holders
Telechat date (None)
Responsible AD Randy Bush
Send notices to <>
A new Request for Comments is now available in online RFC libraries.

        RFC 3627

        Title:      Use of /127 Prefix Length Between Routers
                    Considered Harmful
        Author(s):  P. Savola
        Status:     Informational
        Date:       September 2003
        Pages:      6
        Characters: 12436
        Updates/Obsoletes/SeeAlso:    None

        I-D Tag:    draft-savola-ipv6-127-prefixlen-04.txt


In some cases, the operational decision may be to use IPv6 /127
prefix lengths, especially on point-to-point links between routers.
Under certain situations, this may lead to one router claiming both
addresses due to subnet-router anycast being implemented.  This
document discusses the issue and offers a couple of solutions to the
problem; nevertheless, /127 should be avoided between two routers.

This memo provides information for the Internet community.  It does
not specify an Internet standard of any kind.  Distribution of this
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