[135365] in North American Network Operators' Group
Re: IPv6: numbering of point-to-point-links
daemon@ATHENA.MIT.EDU (bmanning@vacation.karoshi.com)
Mon Jan 24 08:19:30 2011
Date: Mon, 24 Jan 2011 13:18:20 +0000
From: bmanning@vacation.karoshi.com
To: Marco Hogewoning <mch-nanog@xs4all.nl>
In-Reply-To: <4E78852B-1695-4DEE-8B4D-C095446F2AEB@xs4all.nl>
Cc: Lasse Jarlskov <laja@telenor.dk>, nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Mon, Jan 24, 2011 at 02:10:48PM +0100, Marco Hogewoning wrote:
> > While reading up on IPv6, I've seen numerous places that subnets are now
> > all /64.
> >
> > I have even read that subnets defined as /127 are considered harmful.
>
> RFC3627, with a lot of discussion in the IETF on this. See also https://datatracker.ietf.org/doc/draft-ietf-6man-prefixlen-p2p/
>
> > However while implementing IPv6 in our network, I've encountered several
> > of our peering partners using /127 or /126 for point-to-point links.
>
> I personally don't any benefit in using /126 subnets.
>
> > What is the Best Current Practice for this - if there is any?
> >
> > Would you recommend me to use /64, /126 or /127?
> >
> > What are the pros and cons?
>
> >From an operational point of view there is a risk that be using /64 somebody can eat away a lot of memory by either scanning or even changing addresses. This is also described in the draft above...
>
> I would personally recommend to at least always assign the /64, even if you would decide to configure the /127. RFC 3627 has been around long enough that you will keep running into equipment or software that won't like the /127. In which case you can always revert back to /64.
> This will also allow you to use easy to remember addresses like ::1 and ::2, saving you the headache of a lot of binary counting.
>
> Grtx,
>
> Marco
this results in -very- sparse matrix allocation - which is fine, as long as you believe that
you'll never run out/make mistakes. personally, i've use /126 for the past 12 years w/o any
problems.
there was never supposed to be a hard split at /64 - it was done as a means to simplify autoconfig.
--bill
