[131183] in North American Network Operators' Group
=?windows-1252?Q?Re:_IPv6_fc00::/7_=97_Unique_local_addresses?=
daemon@ATHENA.MIT.EDU (Owen DeLong)
Thu Oct 21 04:49:58 2010
From: Owen DeLong <owen@delong.com>
In-Reply-To: <20101021052852.A46E75F0E6C@drugs.dv.isc.org>
Date: Thu, 21 Oct 2010 01:46:55 -0700
To: Mark Andrews <marka@isc.org>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Oct 20, 2010, at 10:28 PM, Mark Andrews wrote:
>=20
> In message <4CBFC1D0.60808@apolix.co.za>, Graham Beneke writes:
>> On 21/10/2010 02:41, Owen DeLong wrote:
>>> On Oct 20, 2010, at 5:21 PM, Jeroen van Aart wrote:
>>>> Someone advised me to use GUA instead of ULA. But since for my =
purposes th
>> is is used for an IPv6 LAN would ULA not be the better choice?
>>>>=20
>>> IMHO, no. There's no disadvantage to using GUA and I personally =
don't think
>> ULA really serves a purpose. If you want to later connect this
>>> LAN to the internet or something that connects to something that =
connects t
>> o something that connects to the internet or whatever, GUA provides
>>> the following advantages:
>>> + Guaranteed uniqueness (not just statistically probable =
uniquene
>> ss)
>>> + You can route it if you later desire to
>>>=20
>>> Since ULA offers no real advantages, I don't really see the point.
>>=20
>> Someone insisted to me yesterday the RFC1918-like address space was =
the=20
>> only way to provide a 'friendly' place for people to start their =
journey=20
>> in playing with IPv6. I think that the idea of real routable IPs on a=20=
>> lab network daunts many people.
>>=20
>> I've been down the road with ULA a few years back and I have to agree=20=
>> with Owen - rather just do it on GUA.
>=20
> Your throwing the baby out with the bath water here.
>=20
> ULA, by itself, is a painful especially when you have global IPv4
> reachability as you end up with lots of timeouts. This is similar
> to have a bad 6to4 upsteam link. Just don't go there.
>=20
> ULA + PA works and provides stable internal addresses when your
> upstream link in down the same way as RFC 1918 provides stable
> internal addressing for IPv4 when your upstream link is down.
>=20
I keep hearing this and it never makes sense to me.
If your provider will assign you a static /48, then, you have stable
addresses when your provider link is down in GUA. Who needs ULA?
> You talk to the world using PA addresses, directly for IPv6 and
> indirectly via PNAT for IPv4. These can change over time.
>=20
Or, if you don't want your IPv6 addresses to change over time, you can
get a prefix from your friendly RIR.
> Similarly, ULA + 6to4 works well provided the 6to4 works when you
> are connected. When your IPv4 connection is renumbered you have a
> new external addresses but the internal addresses stay the same.
>=20
That's a big "provided that"...
One over which you have little or no control unless you are running
a 6to4 gateway of your own and can guarantee that nobody pretends
to be one that is topologically closer to any of your users.
>> I was adding IPv6 to a fairly large experimental network and started=20=
>> using ULA. The local NREN then invited me to peer with them but I=20
>> couldn't announce my ULA to them. They are running a 'public =
Internet'=20
>> network and have a backbone that will just filter them.
>>=20
>> I think that the biggest thing that trips people up is that they =
think=20
>> that they'll just fix-it-with-NAT to get onto the GUA Internet. =
Getting=20
>> your own GUA from an RIR isn't tough - rather just do it.
>=20
> If your big enough to get your own GUA and have the dollars to get
> it routed then do that. If you are forced to use PA (think home
> networks) then having a ULA prefix as well is a good thing.
>=20
home network: 2620:0:930::/48
Try again.
Owen
