Re: Using /126 for IPv6 router links

[Owen DeLong <owen () delong com>]

On Jan 24, 2010, at 4:29 PM, Nathan Ward wrote:

> On 24/01/2010, at 5:28 PM, Leo Bicknell wrote:
>
> > In a message written on Sat, Jan 23, 2010 at 01:52:21PM +0100, Mathias Seiler wrote:
> > > I use a /126 if possible but have also configured one /64 just for the link between two routers. This works great 
> > > but when I think that I'm wasting 2^64 - 2 addresses here it feels plain wrong.
> > >
> > > So what do you think? Good? Bad? Ugly? /127 ? ;)
> >
> > I have used /126's, /127's, and others, based on peers preference.
> >
> > I personally have a fondness for /112's, as it gives you more than
> > 2 addresses, and a DNS bit boundary.
> >
> > For all the pontification about how there are enough /64's to number
> > all the grains of sand, or other nonsense, I think that ignores too
> > much operational information.
> >
> > rDNS is important, and becomes harder in IPv6.  Making it easier
> > is importnat.
> >
> > Having a scan of a /64 fill your P2P T1 is poor design, all because
> > you assigned 2^64 addresses to a link that will never have more
> > than 2 functional devices.
> >
> > Most importantly, we should not let any vendor code any of these
> > into software or silicon, in case we need to change later.
>
> I too prefer /112s. I can take the first /64 in any assignment or allocation and set it aside for networking 
> infrastructure.
> The first /112 is for loopbacks, the remaining /112s are for linknets.
>
> Then I can filter this /64 at my border, and it's easy.
>
> You can do the same thing with /64 linknets, but then you have to set aside a block of them, and that might get hard 
> if you have a /48 or something. Maybe not. What if you have a /56?
If you have link nets, you probably shouldn't have just a /48 and you CERTAINLY shouldn't have just a /56.

Owen