Hi, On Tue, Apr 08, 2014 at 10:34:21PM +0200, Steven Barth wrote: > Hi Gert, > >>i find it very strange that your ISP doesn't offer public addresses on > >>the WAN interface however I think this is actually standards compliant > >>so we have to deal with it. > >It's called "IPv4 exhaustion"... DS-Lite is one of the way to deal > >with it (which effectively gives you "only one NAT in the path"), the > >other way is "hand out RFC1918 or 100.64.* addresses and double-NAT". > > > >Both stinks, but unless someone finds another few billion IPv4 addresses > >somewhere, this is what large scale providers need to do. > I'm sorry but it seems you misunderstood me. We were talking about IPv6 > addresses here.
Indeed, I misunderstood you. I was just returning from yet another
discussion about the unfairness of global IPv4 run-out...
> It seems that Hennings' ISP "only" offers a delegated
> prefix but no global IPv6-address on the WAN-connection (or there is an
> unknown issue acquiring said address which I don't know of). I know that
> RFC 7084 requires a CER to actually deal with this (Weak ES model and
> all) so I added a fix to allow the DS-Lite source endpoint address to be
> acquired from a downstream interface.
There has been quite a bit of discussion in the ISP camp regarding WAN
IPv6 addresses. It's not actually straightforward what to do as an ISP,
so multiple variants exist
- RA for WAN, DHCPv6-PD for LAN
disadvantage: on PPPoE-type deployments, you need two prefixes per
client, one /64 for the WAN-RA, one /56 for DHCP
(but this works quite nicely in cable deployments where you have a
"large shared WAN segment" anyway)
- DHCPv6-IA for WAN, DHCPv6-PD for LAN
disadvantage: extra pool management for WAN needed, basically similar
to RA for WAN
- "require use of an IPv6 address out of the delegated /56 for WAN"
disadvantage: this sort of forces a certain way to segment the /56 onto
the client, so I have not actually seen this in the wild
- run the WAN over link-local only
advantage: only single prefix per customer, easier management for the ISP
(in point-to-point deployment scenarios, like PPPoE)
disadvantage: well, it complicates source address selection on the
CPE, as locally sourced packets leaving via WAN need to use a global
address elsewhere - you named it, already.
gert
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