nanog mailing list archives
Re: IPv6: numbering of point-to-point-links
From: "Crist Clark" <Crist.Clark () globalstar com>
Date: Mon, 24 Jan 2011 16:22:58 -0800
On 1/24/2011 at 5:18 AM, <bmanning () vacation karoshi com> wrote: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 alsohttps://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 somebodycan 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 youwould 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, Marcothis 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.
All of the (mostly religious) arguments about /64 versus any smaller subnets aside, I'm curious about why one would choose /126 over /127 for P-to-P links? Is this some kind of IPv4-think where the all-zeros and all-ones addresses are not usable unicast addresses? This isn't true in IPv6 (of course, it's not strictly true in IPv4 either). Is there another reason? -- Crist Clark Network Security Specialist, Information Systems Globalstar 408 933 4387
Current thread:
- IPv6: numbering of point-to-point-links Lasse Jarlskov (Jan 24)
- Re: IPv6: numbering of point-to-point-links Carlos Friacas (Jan 24)
- Re: IPv6: numbering of point-to-point-links Grzegorz Janoszka (Jan 24)
- Re: IPv6: numbering of point-to-point-links Marco Hogewoning (Jan 24)
- Re: IPv6: numbering of point-to-point-links bmanning (Jan 24)
- Re: IPv6: numbering of point-to-point-links Jack Bates (Jan 24)
- Re: IPv6: numbering of point-to-point-links Crist Clark (Jan 24)
- Re: IPv6: numbering of point-to-point-links Owen DeLong (Jan 24)
- Re: IPv6: numbering of point-to-point-links Randy Bush (Jan 24)
- Re: IPv6: numbering of point-to-point-links Blake Hudson (Jan 31)
- Re: IPv6: numbering of point-to-point-links Randy Bush (Jan 31)
- Re: IPv6: numbering of point-to-point-links Blake Hudson (Jan 31)
- Re: IPv6: numbering of point-to-point-links Randy Bush (Jan 31)
- Re: IPv6: numbering of point-to-point-links bmanning (Jan 24)
- Re: IPv6: numbering of point-to-point-links Gary Buhrmaster (Jan 31)
- Re: IPv6: numbering of point-to-point-links Seth Mattinen (Jan 31)
- Re: IPv6: numbering of point-to-point-links Carlos Friacas (Jan 24)