mailing list archives
Re: Using /126 for IPv6 router links
From: Nathan Ward <nanog () daork net>
Date: Mon, 25 Jan 2010 13:29:21 +1300
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
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
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?
Maybe there is some value in linknets being effectively disposable so you never have to worry about problems coming
from re-use. A single /64 full of /112s gives you 281 trillion.
For links to customers and other networks, I like /64s, because they are right now the standard so you're not going to
run in to compatibility problems. If you've got links to customers you should have a /32, so setting aside a /48 or a
/44 or something for those customer links is no huge drama.
Re: Using /126 for IPv6 router links Glen Turner (Jan 25)
Re: Using /126 for IPv6 router links Leo Bicknell (Jan 24)
Re: Using /126 for IPv6 router links Matthew Petach (Jan 25)
RE: Using /126 for IPv6 router links Pekka Savola (Jan 27)
- Re: Using /126 for IPv6 router links Nathan Ward (Jan 25)