Re: Why ULA: low collision chance (Was: IPv6 fc00::/7 — Unique local addresses)

William Herrin bill at
Fri Oct 22 07:25:10 CDT 2010

On Fri, Oct 22, 2010 at 1:20 AM, Joel Jaeggli <joelja at> wrote:
> On 10/21/10 6:38 PM, Owen DeLong wrote:
>> On Oct 21, 2010, at 3:42 PM, Jack Bates wrote:
>>> On 10/21/2010 5:27 PM, Joel Jaeggli wrote:
>>>> Announce your gua and then blackhole it and monitor your prefix.
>>>> you can tell if you're leaking. it's generally pretty hard to
>>>> tell if you're leaking rfc 1918 since your advertisement may well
>>>> work depending on the filters of your peers but not very far.
>>> This is always the argument I hear from corporate customers
>>> concerning wanting NAT. If  mistake is made, the RFC 1918 space
>>> isn't routable. They often desire the same out of v6 for that
>>> reason alone.
> the rfc 1918 space is being routed inside almost all your adjacent
> networks, so if their ingress filtering is working as expected, great,
> but you're only a filter away from leaking.

A filter away from leaking to -one- of the millions of entities on the
internet. Two filters away from leaking to two.

Bill Herrin

William D. Herrin ................ herrin at  bill at
3005 Crane Dr. ...................... Web: <>
Falls Church, VA 22042-3004

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