RFC 4291, "IP Version 6 Addressing Architecture", February 2006

Note: This RFC has been updated by RFC 5952, RFC 6052, RFC 7136, RFC 7346, RFC 7371, RFC 8064

Errata ID: 8373
Status: Reported
Type: Technical
Publication Format(s) : TEXT
Reported By: Jared Mauch
Date Reported: 2025-04-04

Section 2.5.6 says:

   Routers must not forward any packets with Link-Local source or
   destination addresses to other links.

It should say:

Routers MUST not forward any packets with Link-Local source or destination addresses to other links.  Hop-limit MUST be set to 1.

Notes:

I believe it would be reasonable for someone to override the behavior via setsockopt() call but that the default behavior of an internet connected host should set hlimit=1

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