[racktables-users] Re: IPv6 questions
- From: Tore Anderson <tore.anderson@xxxxxxxxxxxxxxxxxx>
- To: racktables-users@xxxxxxxxxxxxx
- Date: Fri, 01 Apr 2011 15:04:04 +0200
* Tyler J. Wagner
> On Fri, 2011-04-01 at 03:39 +0200, Jeroen ten Berge wrote:
>>> IPv6 subnetting is constrained to nibble boundaries (/32, /36,
>>> /40, ... down to /64). Even if you want to allow arbitrary
>>> subnets (you shouldn't), make that a UI option that defaults to
>>> off. The dragon feature should follow the IPv6 spec.
>
>> I wasn't aware of the nibble boundaries ! Why shouldn't i ?
>
> I spoke too soon. It isn't constrained by the spec to nibbles, but
> in practice, it is. The single best reason is DNS. Breaking PTR
> records within nibble boundaries requires us to use the same hack for
> PTR records as we do for CIDR in IPv4, and nobody wants that.
>
> The spec does specify that an ISP should assign /48's to its
> customers, or at least /56.
While the IETF recommends assigning /48-/56 to end users, this is just a
guideline which is mostly relevant for broadband ISPs, not so much for
data centres and network operators.
It for example quite common to use /127 subnets for point-to-point
links, see <http://tools.ietf.org/html/draft-ietf-6man-prefixlen-p2p>,
so you are wrong about the «in practice» part, too.
Best regards,
--
Tore Anderson
Redpill Linpro AS - http://www.redpill-linpro.com
Tel: +47 21 54 41 27
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