[ppml] IPv6 flawed?

mack mack at exchange.alphared.com
Thu Sep 6 13:41:15 EDT 2007

> Message: 4
> Date: Wed, 5 Sep 2007 18:30:22 -0700
> From: David Conrad <drc at virtualized.org>
> Subject: Re: [ppml] IPv6 flawed?
> To: briand at ca.afilias.info
> Cc: Public Policy Mailing List <ppml at arin.net>
> Message-ID: <AF699AB3-F131-4174-B881-F602A5D93140 at virtualized.org>
> Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
> Brian,
> On Sep 4, 2007, at 11:13 AM, briand at ca.afilias.info wrote:
> > - breaking the hard limit will most likely result in IPv6 getting
> > tossed
> Very true.  An interesting point I hadn't really considered.

In the most relevant products from Cisco (sup32 and sup720) the IPv6 is stored in a TCAM with a different architecture from the IPv4 TCAM.  Specifically the Sup32 and Sup720-3B both have 256000 IPv4 slots and 128000 IPv6 slots.
The IPv4 TCAM on these models will either break or require de-aggregation pruning within the next 6 months.  This de-aggregation pruning could be done in software as part of BGP but is not in the current software (to my knowledge).  The Sup720-3BXL and RSP720-3CXL both have 1000000 IPv4 slots and 512000 IPv6 slots.

This does not cover software based routers or other manufacturers.  Also a large number of models of hardware do not support IPv6 at all.

An argument can be made that it will be cheaper for some organizations to switch to IPv6 shortly due to the impending limit of the FIB TCAM on their routers.

In any case the most relevant Cisco products are going to run out of IPv4 TCAM space before IPv6 even makes a dent.

Someone familiar with the architecture of Juniper and other products should be able to shed light on the capabilities of those products.

LR Mack McBride
Network Administrator
Alpha Red, Inc.

More information about the ARIN-PPML mailing list