need for DHCPv6 [Re: Geoff on IPv4 Exhaustion]

Doug Barton dougb at
Thu Nov 17 02:47:17 CET 2011

On 11/16/2011 15:53, Brian E Carpenter wrote:
> On 2011-11-17 12:05, Doug Barton wrote:
>> On 11/16/2011 14:56, Brian E Carpenter wrote:
>>> On networks I know, including the one I used to
>>> be responsible for so long ago that DHCP was a new feature, *exactly* the
>>> same team controls the routers, the DHCP servers and the DNS servers.
>> I think part of the difference lies in the size of the enterprise in
>> question, and part lies in the evolution of those roles in the "typical
>> enterprise IT shop" over time. The operator community (including me) has
>> been saying for over a decade that IPv6 needs DHCP parity with v4, in
>> part for this exact reason.
> Yes, and I suspect the DHC WG of the IETF would agree with you

Actions speak louder than words.

> (although 'parity' doesn't mean identical options, because the detailed needs
> are different).

Right, that's why I have been using that word carefully.

I said 10 years ago that what we should do is simply copy over all the
relevant options from DHCP for IPv4. I was told that it wasn't necessary
because what would happen is that if an option was relevant, someone
would write a draft and make it happen. Oooooooookey dokey. Nice plan
(?!?) but it didn't quite work out that way.

> The intention, as I recall it, of starting off in IPv6
> by defining RA, ND and SLAAC was to allow plug-and-play for simple, and
> possibly disconnected, networks.

Personally, I always thought that was a solution looking for a problem.
However that plan also included, "RA for routing only, DHCP for
everything else."

> What we keep arguing about is the exact scale of network above which
> DHCPv6 is a necessity. I'm not even sure that's an argument worth
> having.

But, it is. Because by not following the original plan (however
misguided) we've gotten into the mess that mif is currently trying to
deal with regarding reconciling conflicting DNS config information from
DHCP and RA. That should never have been allowed to happen, and many of
us tried to explain (in nauseating detail) why it was a bad idea.

The rational path has always been RA for routing only, and parity for
DHCP (including network/gateway/etc., IOW, "DHCPv6 only"). Obviously the
former is now unattainable, but the latter should be done ASAP.



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