Subject: Re: RA "requires" DHCPv6 ?

From: Fernando Gont <[email-masked]>
Date: Sun, 01 Apr 2012 14:57:29 +0200

On 04/01/2012 12:46 AM, Karl Auer wrote:
> On Sat, 2012-03-31 at 21:43 +0200, Fernando Gont wrote:
>>> Or you could use one's statically assigned address. 
>>
>> Oh, yeah. And you could have opted to not send the RS in the first
>> place... and what? :-)
> 
> Um, I'm not sure why we're arguing. I'll still see unsolicited RAs at
> regular intervals, and I'll see RAs sent because of other hosts' RSes.
> Also, the RA contains lots of useful stuff even if I am not doing DHCPv6
> - for example if I want to do SLAAC I'll still be sending an RS. I don't
> think my question was stupid. I'm sorry you do.

I'm not saying that your question is stupid. I'm just saying that
regardless of whether there's a SHOULD/MUST in the RFCs regarding doing
DHCPv6, truth is that you should be prepared to do it, because if the
local router wants you to do DHCPv6, you essentially have no option.

>> -- However, particularly in the case in which the local router wants
>> you to use DHCPv6, they could easily block addresses that have not
>> been leased by the DHCPv6 server. SO, at the end of the day, you're at
>> its mercy.
> 
> Absolutely. The question was just whether or not a host was *required*
> "O" flags and do DHCPv6, not whether it would be practical or
> appropriate to do so.

Well, if you mean "required" in the sense of MUST, then probably not.
But if you mean "required" as in "do you need to do DHCPv6 to get
Internet connectivity?", then the answer is "Most likely, Yes".

> And I was not saying you were wrong - I was seeking clarification (from
> you or anyone), because IMHO it is not clear from the RFCs whether a
> host SHOULD or MUST honour the "M" and "O" flags (obviously it MAY :-). 

I should double-check that. But if the RA has the "M" bit, then at least
in that case you should do DHCPv6, even if the RFCs do not say so. If
there's no "MUST" or "SHOULD" for that (which I don't recall of the top
of my head), I guess that MUST/SHOULD has more to do with whether
there's a formal requirement for every host to implement DHCPv6, than
anything else. BUt then, as with the requirement to implement IPsec,
that's, IMO, mostly "words on paper".

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: [email-masked]
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