nanog mailing list archives
Re: IPv6 fc00::/7 — Unique local addresses
From: Owen DeLong <owen () delong com>
Date: Thu, 21 Oct 2010 01:46:55 -0700
On Oct 20, 2010, at 10:28 PM, Mark Andrews wrote:
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 this is used for an IPv6 LAN would ULA not be the better choice?IMHO, no. There's no disadvantage to using GUA and I personally don't thinkULA really serves a purpose. If you want to later connect thisLAN to the internet or something that connects to something that connects to something that connects to the internet or whatever, GUA providesthe following advantages: + Guaranteed uniqueness (not just statistically probable uniqueness)+ You can route it if you later desire to Since ULA offers no real advantages, I don't really see the point.Someone insisted to me yesterday the RFC1918-like address space was the only way to provide a 'friendly' place for people to start their journey in playing with IPv6. I think that the idea of real routable IPs on a lab network daunts many people. I've been down the road with ULA a few years back and I have to agree with Owen - rather just do it on GUA.Your throwing the baby out with the bath water here. 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. 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.
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.
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.
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 using ULA. The local NREN then invited me to peer with them but I couldn't announce my ULA to them. They are running a 'public Internet' network and have a backbone that will just filter them. I think that the biggest thing that trips people up is that they think that they'll just fix-it-with-NAT to get onto the GUA Internet. Getting your own GUA from an RIR isn't tough - rather just do it.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.
home network: 2620:0:930::/48 Try again. Owen
Current thread:
- IPv6 fc00::/7 — Unique local addresses Jeroen van Aart (Oct 20)
- Re: IPv6 fc00::/7 — Unique local addresses Jay Ford (Oct 20)
- Re: IPv6 fc00::/7 — Unique local addresses Mark Smith (Oct 20)
- RE: IPv6 fc00::/7 — Unique local addresses Deepak Jain (Oct 20)
- Re: IPv6 fc00::/7 — Unique local addresses Jeroen van Aart (Oct 20)
- Re: IPv6 fc00::/7 — Unique local addresses Owen DeLong (Oct 20)
- Re: IPv6 fc00::/7 — Unique local addresses Graham Beneke (Oct 20)
- Re: IPv6 fc00::/7 — Unique local addresses Mark Andrews (Oct 20)
- Re: IPv6 fc00::/7 — Unique local addresses Owen DeLong (Oct 21)
- Re: IPv6 fc00::/7 — Unique local addresses Ben Jencks (Oct 21)
- Re: Re: IPv6 fc00::/7 — Unique local addresses Mark Andrews (Oct 21)
- Re: IPv6 fc00::/7 — Unique local addresses Owen DeLong (Oct 21)
- Re: Re: IPv6 fc00::/7 — Unique local addresses Mark Andrews (Oct 21)
- RE: IPv6 fc00::/7 — Unique local addresses Deepak Jain (Oct 20)
- Re: IPv6 fc00::/7 — Unique local addresses Karl Auer (Oct 21)
- RE: IPv6 fc00::/7 - Unique local addresses Skeeve Stevens (Oct 21)
- RE: IPv6 fc00::/7 - Unique local addresses Karl Auer (Oct 21)
- RE: IPv6 fc00::/7 - Unique local addresses Skeeve Stevens (Oct 21)
- Re: IPv6 fc00::/7 - Unique local addresses Owen DeLong (Oct 21)
- Re: IPv6 fc00::/7 - Unique local addresses Mark Andrews (Oct 21)