Companies using public IP space owned by others for internal routing

William Herrin bill at
Mon Dec 18 23:09:16 CST 2017

On Sun, Dec 17, 2017 at 11:31 PM, Eric Kuhnke <eric.kuhnke at> wrote:

> some fun examples of the size of ipv6:
> 2qxgxw/self_just_how_big_is_ipv6/

Hi Eric,

Lies, damn lies and statistics. Both projections assume that IPv6 addresses
are assigned the same way we assign IPv4 addresses. They are not.

There are several practices which consume IPv6 at a drastically higher rate
than IPv4. The most notable is the assignment of a /64 to every LAN. Your
/26 LAN that used to consume 2^6th IP addresses? Now it's 2^64th. Used to
consume RFC1918 addresses? Now it's 2^64th of the global IPv6 addresses.

Why did we need a /64 for each LAN? So we could incorporate the Ethernet
MAC address in to the IP address. Only we can't actually do that because it
turns out to be crazy insecure. Nevertheless, the 3 computers in your
basement will still consume 2^64th IPv6 addresses between them. But hey,
what's 20 orders of magnitude between friends.

We have ISPs that have received allocations of entire /19s. A /19 in IPv6
is exactly the same percentage of the total address space as a /19 in IPv4.
Before considering reserved addresses, it's 1/2^19th of the total address
space. For a single ISP. Think about it.

Meanwhile the IETF has learned nothing from the gargantuan waste that is ($2billion at current prices). They went and assigned FC00::/7.
 /7!! Almost 1% of the IPv6 address space gone in a single RFC.

I haven't attempted to compute the actual rate of IPv6 consumption but it's
not inconceivable that we could exhaust them by the end of the century
through sheer ineptitude.

On the plus side, we're mostly only screwing around with 2000::/3 right
now. After we burn through that in the next 20 years, we can if we so
desire change the rules for how (and how quickly) we use 4000::/3.

Bill Herrin

William Herrin ................ herrin at  bill at
Dirtside Systems ......... Web: <>

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