Date: Fri, 19 Nov 2004 10:11:36 -0800
From: Crist Clark <firstname.lastname@example.org>
Lars Erik Gullerud wrote:
>>/127 prefixes are assumed for point-to-point links, and presumably an
>>organization will divide up a single /64 for all ptp links -- unless they
>>have more than 9,223,372,036,854,775,808 of them.
> While that would seem logical for most engineers, used to /30 or /31 ptp
> links in IPv4 (myself included)
Aren't most engineers used to the fact that point-to-point links are
not broadcast links and therefore the concept of a network/netmask for
the interface is somewhat useless? In addition, link-local addressing
eliminates many situations where you need to allocate tiny blocks for
Just to introduce a touch of practicality to this discussion, it might
be worth noting that Cisco and Juniper took the RFC stating that the
smallest subnet assignments would be a /64 seriously and the ASICs only
route on 64 bits. I suspect that they influenced the spec in this area as
expending them to 128 bits would have been rather expensive.
In any case, if the prefix length is >64, routing is done in the
CPU. IPv6 traffic for most tends to be light enough that this is not a
big issue today, but the assigning /126 or /127s for P2P links is
really, really not a good idea. the use of 127s also ignore the
possibility of a anycast address.