[148888] in North American Network Operators' Group
Re: Choice of address for IPv6 default gateway
daemon@ATHENA.MIT.EDU (Owen DeLong)
Wed Jan 25 18:45:42 2012
From: Owen DeLong <owen@delong.com>
In-Reply-To: <CALFTrnNxrn2szA=AsfFZaKD34OQVJVGQ_B_7oqOcMqWnnZZjuQ@mail.gmail.com>
Date: Wed, 25 Jan 2012 15:39:52 -0800
To: Ray Soucy <rps@maine.edu>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Jan 25, 2012, at 8:40 AM, Ray Soucy wrote:
> On Wed, Jan 25, 2012 at 10:06 AM, Leo Bicknell <bicknell@ufp.org> =
wrote:
>=20
>> I don't think the industry has really found a best practice to
>> document yet. There are people trying different ideas. We find
>> the following convention allows us to keep things organized:
>>=20
>> <prefix>::1 - Default gateway
>> <prefix>::<last octect IPv4> - Statically assigned servers.
>> <prefix>:<eui-64> - Auto-configured host
>=20
> This is essentially what we do (except we use the hex value of the
> last octet, so .34 would be ::22, probably just the purist in me).
>=20
Having done both hex-conversion and BCD (in fact I mention both =
possibilities in the IPv6 courses that I teach), I have to say that the =
purist loses to the pragmatist in my mind and BCD makes much more sense. =
You can, actually, safely BCD up to the last three IPv4 octets in an =
IPv6 address without violating the 12-bits of zeroes rule to avoid =
EUI-64 collisions, so, for example, 10.1.2.3 could become =
<prefix>::1:2:3, or, 10.209.198.144 could be <prefix>::209:198:144.
> If you have an environment where hosts will be statically configured,
> then you probably want to use a global default, if only to avoid
> confusion from users or poorly written software that expects the
> default to be in the same prefix as the address.
>=20
Well, any software should be able to handle a link-local default, but, =
otherwise, yes.
> If people understand their prefix is 2001:DB8::/64, and the gateway is
> 2001:DB8::1 it raises a lot less questions than "your prefix is
> 2001:DB8::/64 but your default router is FE80...".
>=20
People will have to get used to the fe80 thing pretty quickly anyway, =
since that's what you get with RAs regardless.
Owen
