Re: DHCPv6 address used when M or O bit is set

Dominik Elsbroek <> Wed, 04 April 2012 14:38 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 74B7821F8657 for <>; Wed, 4 Apr 2012 07:38:47 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -3.599
X-Spam-Status: No, score=-3.599 tagged_above=-999 required=5 tests=[BAYES_00=-2.599, RCVD_IN_DNSWL_LOW=-1]
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id H49bR-9D3veT for <>; Wed, 4 Apr 2012 07:38:46 -0700 (PDT)
Received: from ( []) by (Postfix) with ESMTP id 4332221F86B0 for <>; Wed, 4 Apr 2012 07:38:46 -0700 (PDT)
Received: by iazz13 with SMTP id z13so526808iaz.31 for <>; Wed, 04 Apr 2012 07:38:46 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=LisaTDjUXDEiMCv2XT3RL6gvbOJ9aipZN5cwQgmMtdY=; b=ol4RTH5+LMuBh9RYZ0+VbeYXBm0Nc9vcqZubSFKNxdzPbayK28TzsNDguOSXuwnchj iqjVj5pRrl+jl25YXQz7cWi3lpONXBlsOfGUhLCHEIvNWQJKC6k7qza/ly0pqDuAvqar tuuMyQY8PfO24KM/gQaMGeyD2LGLH83KcRCKX857tHTMhO5FPqrWTk3GdwFd5d16MUBw 2sPTflYLrLxJBqcD+2KdkECJeIEKeNxVpzjhZDbHW7QkAMLhKuuB1mlb7RhvjCCKMoLa DpR2iARKDEDCOIH6l4wd6m7ulVDNNpy4mw94V+2f9oXctdIyKCzOlGBA/ym7i+wkZ9we dkhQ==
MIME-Version: 1.0
Received: by with SMTP id ge5mr1795875igb.21.1333550325954; Wed, 04 Apr 2012 07:38:45 -0700 (PDT)
Received: by with HTTP; Wed, 4 Apr 2012 07:38:45 -0700 (PDT)
In-Reply-To: <>
References: <> <>
Date: Wed, 4 Apr 2012 16:38:45 +0200
Message-ID: <>
Subject: Re: DHCPv6 address used when M or O bit is set
From: Dominik Elsbroek <>
To: Fernando Gont <>
Content-Type: text/plain; charset=ISO-8859-1
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: "IPv6 Maintenance Working Group \(6man\)" <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Wed, 04 Apr 2012 14:38:47 -0000

Hi Fernando,

> What's removed is the corresponding text, not the bits. See page 19 of
> RFC 4861: the bits are still there.

In RFC4862, Appendix C there is one point:

Removed the text regarding the M and O flags, considering the
      maturity of implementations and operational experiences.
      ManagedFlag and OtherConfigFlag were removed accordingly.  (Note
      that this change does not mean the use of these flags is

Not sure how to interprete this. Perhapts I am just missing a link,
but M and O flag in RFC 4861 doesn't tell how to do SLAAC, e.g. when
the nameserver should be determined by DHCPv6-server.

>> They don't even longer exist, but still
>> exist?
> I'm curious about why the corresponding text was removed. In particular
> when at the time (2007) the DNS options was not yet widely implemented,
> and hence you *needed* DHCPv6 to learn the addresses of recursive DNS
> servers dynamically.

I am still very curious which address a client should use, if the O or
M flag is set, to find a DHCPv6 server.