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Re: IPv6 routes, was: How Not to Multihome

  • From: Keegan . Holley
  • Date: Mon Oct 08 20:15:39 2007

Mike Leber <[email protected]> wrote on 10/08/2007 07:36:56 PM:

> 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

Wouldn't resources still be an issue.  Since the address space is so much larger wouldn't the 235k v6 routes take up more than 4 times the router memory?
> 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.

What about MPLS?  The last time I poked around in one of the core routers there were about 1.2 million routes.  This includes all the private space that is routed between different sites in the same vpn and customers that use overlapping IP space.  I had always assumed the routing tables would be massive under IPv6.

> *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?

Can I interest you in some used M40's?

> 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.

Well I guess I can nix that rootkit for IP enabled cukoo clocks. : )