[175225] in North American Network Operators' Group
Re: IPv6 Default Allocation - What size allocation for Loopback
daemon@ATHENA.MIT.EDU (William Herrin)
Sun Oct 12 18:01:36 2014
X-Original-To: nanog@nanog.org
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In-Reply-To: <1070171971.148616.1413006103313.JavaMail.zimbra@snappytelecom.net>
From: William Herrin <bill@herrin.us>
Date: Sun, 12 Oct 2014 18:00:57 -0400
To: Faisal Imtiaz <faisal@snappytelecom.net>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
On Sat, Oct 11, 2014 at 1:41 AM, Faisal Imtiaz <faisal@snappytelecom.net> wrote:
> A follow up question on this topic..
>
> For Router Loopback Address .... what is wisdom in allocating a /64 vs /128 ?
> (the BCOP document suggests this, but does not offer any explanation or merits of one over the other).
Hi Faisal,
One of the viewpoints held by some in the IETF is that an IPv6 address
is not 128 bits. Rather, it is 64 bits of network space and 64 bits of
host space. I'm told this viewpoint is responsible for the existence
of a 128 bit address instead of IPv6 using 64 bit addresses.
If you follow that reasoning, the subnet mask should always be /64, no
matter where the address is assigned.
There are, of course, excellent operational reasons not to religiously
follow that plan.
Regards,
Bill Herrin
--
William Herrin ................ herrin@dirtside.com bill@herrin.us
Owner, Dirtside Systems ......... Web: <http://www.dirtside.com/>
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