[131658] in North American Network Operators' Group
Re: Failover IPv6 with multiple PA prefixes (Was: IPv6 fc00::/7
daemon@ATHENA.MIT.EDU (Mark Andrews)
Sun Oct 31 22:44:03 2010
To: Christopher Morrow <morrowc.lists@gmail.com>
From: Mark Andrews <marka@isc.org>
In-reply-to: Your message of "Sun, 31 Oct 2010 21:29:27 EDT."
<AANLkTimsB6Uj-jpogLg08Q-RZDUB-+C9c5KMzcKTQKmQ@mail.gmail.com>
Date: Mon, 01 Nov 2010 13:43:39 +1100
Cc: NANOG list <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
In message <AANLkTimsB6Uj-jpogLg08Q-RZDUB-+C9c5KMzcKTQKmQ@mail.gmail.com>, Chri
stopher Morrow writes:
> On Sun, Oct 31, 2010 at 2:01 PM, George Bonser <gbonser@seven.com> wrote:
> >> ula really never should an option... except for a short lived lab,
> >> nothing permanent.
> >
> > I have a few candidate networks for it. =A0Mostly networks used for
> > clustering or database access where they are just a flat LAN with no
> > "gateway". =A0No layer 3 gets routed off that subnet and the only things
> > talking on it are directly attached to it.
>
> why not just use link-local then?
If you had actually every tried to use link-local then you would know why
you don't use link-local.
> eventually you'll have to connect
> that network with another one, chances of overlap (if the systems
> support real revenue) are likely too high to want to pay the
> renumbering costs, so even link-local isn't a 100% win :(
> globally-unique is really the best option all around.
2^40 is 1099511627776. The chances of collision are so low that
one really shouldn't worry about it. You are millions of times
more likely of dieing from a asteroid 1-in-500,000[1].
If you merge thousands of ULA and don't consolidate then you start
to have a reasonable chance of collision. Even if you do have
colliding ULA prefixes you don't necessarially have colliding subnets
when merging companies. Just allocate subnet randomly. It's not
like 2^16 internal subnets is going to be a major routing problem.
Mark
[1] http://www.livescience.com/environment/050106_odds_of_dying.html
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: marka@isc.org
