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[IPv6]Re: [v6ops] New draft: "The IPv6 Loopback Address Prefix"

Michael Sweet <msweet@msweet.org> Thu, 27 November 2025 15:59 UTC

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From: Michael Sweet <msweet@msweet.org>
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Date: Thu, 27 Nov 2025 10:58:49 -0500
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To: Brian E Carpenter <brian.e.carpenter@gmail.com>
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CC: Ole Trøan <otroan.ietf@gmail.com>, Gert Doering <gert@space.net>, Geoff Huston <gih902@gmail.com>, IPv6 <ipv6@ietf.org>, IPv6 Operations <v6ops@ietf.org>
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Subject: [IPv6]Re: [v6ops] New draft: "The IPv6 Loopback Address Prefix"
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Brian,

> On Nov 26, 2025, at 11:14 PM, Brian E Carpenter <brian.e.carpenter@gmail.com> wrote:
> 
> Michael,
> 
> On 27-Nov-25 10:47, Michael Sweet wrote:
>> Brian,
>>> On Nov 26, 2025, at 3:25 PM, Brian E Carpenter <brian.e.carpenter@gmail.com> wrote:
>>> ...
>>> (d) as far as my experiments went, mDNS on Linux has messed up support for link-local addresses, which all need a zoneid because of (b). Which is probably the real reason that ::/96 would work on Linux virtual interfaces but fe80::/10 wouldn't.
>> I haven't noticed any particular issues with my Linux laptop or VMs using Avahi, although for my home office the Wi-Fi and Ethernet are treated as a single LAN (Ubiquity DM Pro + a bunch of APs and switches) so it is possible I am just "lucky".  
> 
> The problems that I saw are described in the README at https://github.com/becarpenter/misc/tree/main/zelect

Avahi doesn't want to compete with another mDNS resolver on the same machine, so I think your observations can be distilled down to "ping6 and Chrome don't handle IPv6LL addresses obtained via mDNS".  I can dig a bit to see where the breakage is happening - more than likely the numeric address is getting copied without the zone ID, leading to the failure.

FWIW, Linux support for IPv4LL is also problematic - it works but not all of the implementations (there are several...) actually implement RFC 3927 correctly.

________________________
Michael Sweet

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