Link local for P-t-P links? (Was: IPv6 prefixes longer then /64: are they possible in DOCSIS networks?)

Jeff Wheeler jsw at
Thu Dec 1 08:36:13 UTC 2011

On Wed, Nov 30, 2011 at 9:15 PM, Mike Jones <mike at> wrote:
> Link-Local?
> For "true" P-t-P links I guess you don't need any addresses on the

Point-to-point links in your backbone are by far the easiest thing to
defend against this attack.  I wish we would steer the discussion away
from point-to-point links that are entirely within the control of the
operator, as this is really quite well understood.  Major ISPs
including Level3 are already doing /126 to their customers today as
well.  In fact, Level3 does not even reserve a /64, they will hand out
::0/126 to one customer on a given access router, ::4/126 to the next.
 It clearly works.

The access layer for non point-to-point customers, on the other hand,
is less well-understood.  That's why we keep having these discussions.
 Getting customers (and their device/software) to work correctly with
link-local addressing and DHCP-PD or similar is going to be an uphill
battle in a hosting environment.  It also breaks down immediately if
the hosting customer, for example, wishes to use ND to be able to
provision addresses on two or more servers from a common subnet.  So
there are both perception and practical problems / limitations with
this approach.  I'm not saying it's a bad idea, but it won't work in
some instances.

Jeff S Wheeler <jsw at>
Sr Network Operator  /  Innovative Network Concepts

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