On 10/12/14 3:00 PM, William Herrin wrote:
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.
https://tools.ietf.org/html/rfc6164 Is a standards track document. it is imho a repudiation of the assumptions about the dimensions of the host field.
There are, of course, excellent operational reasons not to religiously follow that plan.
Regards, Bill Herrin