Re: IPv6 certification - IPv6 Router Advertisement Lifetime 0 and Reachable time 10 seconds

Isaac <> Sun, 24 January 2021 16:07 UTC

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From: Isaac <>
Date: Sun, 24 Jan 2021 21:37:17 +0530
Message-ID: <>
Subject: Re: IPv6 certification - IPv6 Router Advertisement Lifetime 0 and Reachable time 10 seconds
To: Nick Hilliard <>
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Thanks Nick for the timely response!!!

I understand your comment regarding the prerogative of IPv6 forum in this
regard. Meanwhile, we need a technical answer/analysis of the combination
of RA lifetime 0 and Reachable time 10s whether that makes sense or whether
it was clearly envisioned in the original IPv6 design. We know that RFC
puts forth a set of 'may', 'might' conditions which are deemed optional in
certian corner cases (possibly). We are already having discussions with the
certification body but we need to go with a clear cut technical response of
whether RA lifetime 0 and reachable time 10 seconds makes sense or not.
Same way, section 6.2.3 in RFC4861 puts forth a 'might' condition. RA with
a lifetime 0 and with advertised prefixes might mean that there may be a
second router in the LAN segment which advertises a positive lifetime. And
this itself is a corner scenario we believe and common scenario would be a
single router in a LAN segment who always advertises with a positive
lifetime until he decides to cease to be default gatewway for clients
(probably he is ging down as well). But the combination of RA lifetime 0
and reachable time 10 seconds doesn't make sense to us and we are clueless
as to how that can be supported. We do not want to deisgn some throw away
logic just for certfication purpose and we do think thats neither the
purpose of certification bodies nor the end customers. We need a solid
technical answer from the IETF IPv6 official body in this regard. Please
review and respond.


On Sun, Jan 24, 2021 at 5:38 PM Nick Hilliard <> wrote:

> Isaac wrote on 24/01/2021 11:02:
> > At the moment, we are unable to find a scenario (real world usecase) to
> > support RA lifetime of 0 and RA reachable time of 10 seconds. Please
> > review and respond.
> Isaac,
> you're referring to an IPv6 Forum document, so they might be more
> qualified to give an answer to your question.
> As a potential pointer, rfc4861 documents the following case in section
> 6.2.3:
> >    A router might want to send Router Advertisements without advertising
> >    itself as a default router.  For instance, a router might advertise
> >    prefixes for stateless address autoconfiguration while not wishing to
> >    forward packets.  Such a router sets the Router Lifetime field in
> >    outgoing advertisements to zero.
> Nick