/127 between routers?

[Tim Durack]

On Mon, Jan 11, 2010 at 2:55 PM,  <sthaug at nethelp.no> wrote:
>> The opposite was indicated to me by Cisco; that on the CRS-1 masks > 64
>> bits would slow the pps throughput of the ASIC. That statement would in
>> turn affect loopbacks, too... no more /128s? Meanwhile, 7600s were
>> explicitly mentioned as not being affected in this same way.
>
> I would definitely be sceptical of any such CRS-1 claims until some
> supporting evidence can be produced.
>
>> I think if you use anything other than /64s, there will be bumps on the
>> road ahead for you.
>
> That train left the station long ago.
>
> Steinar Haug, Nethelp consulting, sthaug at nethelp.no
>

This thread has definitely provided food for thought.

We have currently deployed /128s on loopbacks, and /112s on ptp,
assigned from a site infrastructure /48. /64s are used on everything
else, assigned from a per-site "customer" /48. That maintains a clean
separation between infrastructure and customer space, something that
has been sorely missing from our IPv4 deployments.

The ARIN wiki (http://www.getipv6.info/index.php/IPv6_Addressing_Plans)
encourages this kind of address plan.

rfc4291 is quite clear that only /64s should be used on interfaces.
rfc3627 acknowledges the operational reality that other lengths can
and are being used on ptp interfaces (/127, /126, /120, /112.)

That leaves me in a state of confusion.

I could assign /64s per ptp without difficulty. Should I also assign
/64s per loopback? Should I really being using some form of EUI-64 for
these addresses, to guarantee the interface ID is unique no matter
what the network prefix? What happens when I replace hardware and
EUI-64 changes ptp/loopback addresses?

I'm sure others have gone through this same mental (and design/ops) exercise.

-- 
Tim:>
Sent from Brooklyn, NY, United States