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Re: IPv6 routes, was: How Not to Multihome

  • From: Mike Leber
  • Date: Mon Oct 08 19:40:07 2007

On Mon, 8 Oct 2007 [email protected] wrote:
> I'm really interested to see what happens when we start filling those same 
> routers with ipv6 routes.

Well, IPv6 prefixes will eventually be some number between the total
number of ASes in use (which represents the number of networks that can
afford and desire to run BGP) and the number of IPv4 prefixes in use
(which represents the number of customers that can afford, justify, and
desire to get address space).

So today, if IPv6 was instantly ubiquitously deployed by every network on
the planet that runs IPv4: you would would see between 26,249 and 235,174
IPv6 routes (data from

You bought or are planning to buy core routers that support IPv6 at
wirespeed in hardware didn't you?

If you are (or plan to be) operating an IPv4 network for over 5 years (let
alone the folks here that can say 10 or 15+ years), you are planning core
router purchases on a cycle like 3 to 5 years by estimating what you need
at the end of that time and then specifying accordingly.

By looking at the graph at the top of the page for total route announcements you could
make a wild guess that if you want a router that has a high probability of
working without needing workarounds (or giving you unnecessary headaches)
in 3 years it needs to handle 500,000 IPv4 routes and 500,000 IPv6 routes
in hardware when you buy it.  Arguably this is overkill for IPv6, and
might last 5 to 7 years.

*All* the core router vendors (Cisco, Juniper, Foundry, Force10, etc) sell
routers that can do this today.  If you are buying something that can't
handle the 3 year IPv4 requirement, let alone the IPv6 requirement, why
are doing that to yourself?

Contrary to what seems to be popular misconception, your refrigerator
will not be multihomed under IPv6.  There are dynamic economic pressures
(such as consolidation, competition, effective regulatory monopoly, etc)
that limit the number of networks in the global routing table.


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