So Philip Smith / Geoff Huston's CIDR report becomes worth a good hard look today

Geoff Huston gih at
Wed Aug 13 23:37:06 UTC 2014

On 14 Aug 2014, at 4:14 am, Paul Ferguson <fergdawgster at> wrote:

>> On 8/13/14 8:55 AM, Paul Ferguson wrote:
>>> Apologies for replying to my own post, but... below:
>>> On 8/13/2014 7:05 AM, Paul Ferguson wrote:
>>>> p.s. I recall some IPv6 prefix growth routing projections by
>>>> Vince Fuller and Tony Li from several years ago which
>>>> illustrated this, but cannot find a reference at the
>>>> moment....

I shared some speculation on the next five years of routing table growth at NANOG 60.

BGP routing table growth has been remarkably stable for many years, and most of the older predictive exercises have proved to be reasonably accurate.  with all the usual caveats applying to a post-V4-exhaustion world having a lot more uncertainties than before the current figures show that the default free zone in IPv4 will hit 1 million entires in 2019 ( slide 30).

IPv6 is a much less certain exercise. If we take the most extreme picture of of the recent past and apply en exponential growth model to the IPv6 network, then the V6 table gets to 125,000 entries by the same 2019. (slide 34 of the same pack)

Frankly, these figures are not particularly alarming at present. Yes, we've crossed over some equipment thresholds in the past (TCAM banks of 256K entires, now 512K and at some point its looking possible that we'll get to 1M entries. If yesterday is a lot like tomorrow then this is some 4 years out for the global routing table if we add the IPv4 and IPv6 tables together.

If I were buying equipment today I'd want a minimum of 2M entries in the TCAM on the forwarding cards, and I'd also want to understand my options for field upgrades to at least 4M over the anticipated operational lifecycle of the equipment. But you may have a different crystal ball of course.


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