Re: RA "requires" DHCPv6 ?

Fernando Gont <> Sat, 31 March 2012 12:50 UTC

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Date: Sat, 31 Mar 2012 14:10:04 +0200
From: Fernando Gont <>
Organization: SI6 Networks
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To: Karl Auer <>
Subject: Re: RA "requires" DHCPv6 ?
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Hi, Karl,

On 03/31/2012 12:57 AM, Karl Auer wrote:
> In a discussion titled "Stable privacy addresses (upcoming rev)",
> Fernando Gont said:
>> They could [...] have RAs require you to do DHCPv6 and then have
>> DHCPv6 assign you a constant address, etc.
> What interests me here is the phrase "have RAs require you to do DHCPv6".

If the RAs do not include PIOs, and have the "M" bit set, what are your

1) Do DHCPv6, or,
2) Go to the park, and enjoy some sun, because "no internet today".

> There was a bunch of stuff about the M and O flags in RFC2462, almost
> all of which was removed in RFC4862. In RFC2462, the word
> "should" (*not* capitalised) was used, along with phrases like "is to
> be".
> Then there is RFC 4861 (neighbor discovery) which says:
>       M              1-bit "Managed address configuration" flag.  When
>                      set, it indicates that addresses are available via
>                      Dynamic Host Configuration Protocol [DHCPv6].
> [...]
>       O              1-bit "Other configuration" flag.  When set, it
>                      indicates that other configuration information is
>                      available via DHCPv6.
> Anyway, I've been working on the basis that the M and O flags are
> advisory and not prescriptive. That is, they do not *require* the host
> to do anything.

Exactly: They do not REQUIRE you to do DHCPv6. You MAY want  not to do
it, and just not use the Internet for the day.

Fernando Gont
SI6 Networks
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