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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Stupid Ipv6 question...
> Date: Fri, 19 Nov 2004 10:11:36 -0800 > From: Crist Clark <[email protected]> > Sender: [email protected] > > > Lars Erik Gullerud wrote: > > > On Fri, 2004-11-19 at 16:36, Stephen Sprunk 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 > p2p links. 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. -- R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: [email protected] Phone: +1 510 486-8634
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