IPv6 prefixes longer then /64: are they possible in DOCSIS networks?

Leo Bicknell bicknell at ufp.org
Thu Dec 1 03:27:17 UTC 2011

In a message written on Wed, Nov 30, 2011 at 07:19:51PM -0500, Ray Soucy wrote:
> There is a lot of talk about "buggy" systems that are unable to handle
> prefixes longer than 64; but I've yet to encounter one.  I imagine if

This has been one of the first thing I tested with new router gear
for, well, a decade or more now of IPv6 testing.  I too have never
encountered such a box, even in the early days of IPv6.  I think
if any such boxes were made they were likely prototypes and never
sold in quantity.

There was a different, but related problem early on.  Platforms
with 32-bit TCAM that had to be retrofitted for IPv6 had to do
multiple lookups.  Two lookups got you 64 bits, and since 64 bits
was the "longest subnet" they did dumb things past that bit boundary.
This could result in less than line rate performance of IPv6 frames.

I'm honestly having trouble remembering which platforms had this
issue, perhaps someone remembers better than I do.  However, I do
think my lack of memory is in part because I haven't encountered
one in a network anytime recently...

In short, a total non-issue in terms of IPv6 deployment today.

       Leo Bicknell - bicknell at ufp.org - CCIE 3440
        PGP keys at http://www.ufp.org/~bicknell/
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