dhcpcd-discuss

Ah, that has also got its RFC update: RFC 6164 Using 127-bit IPv6 prefixes on inter-router links. Yes, that's possible. The RFC also clearly describes the issues you get and why most reasons for /127 are already moot.
What I think we're seeing here is that politics are more and more driving the IPv6 technology stack in a certain direction, whether we like or not. Basically, IPv6 follows the money -- not that surprisingly. And DHCPv6 seems to be kind of roadkill especially in view of the Digitalization tzunami now swapping...

So I would like to cite the renown German security researcher Enno Rey here, with his "[no] deviation from defaults". It's (/127 instead of /64) doable, but in the long run you might get thrown under the wheels when not keeping to the main pavewalk.
The DHCPv6 office guys are already feeling the heat: Android won't implement DHCPv6 for the reasons commonly brought forward by office IT stuff, because it's not worth the hassle for a Google which makes money on a much bigger scale from having as many devices always connected ... and office IT is just too tiny a group. There have been enterprise "big fishes" asking from Android DHCPv6 and simply got no answer at all from Google. That's as good an answer as well.
But when doing such inter-router links, either do them manually (which is out of RFC scope anyway), so you can configure a /127 prefix together with the address, or simply use DHCPv6 PD and its address generation for the downstream interface.
Because that's a deviation from default, large-scale PD such as with all-IP home ADSL connections, often deploys DHCPv6 PD on /56 or /60, and uses SLAAC(!!) for all upstream and downstream interfaces. There will be other configurations as well, but this is what I see over here.
Best regards,
Harald


-------- Ursprüngliche Nachricht --------Von: "Neal P. Murphy" <neal.p.murphy@xxxxxxxxxxxx> Datum: 29.09.17  12:12  (GMT+01:00) An: dhcpcd-discuss@xxxxxxxxxxxx Betreff: Re: [dhcpcd-discuss] DHCPv6 addresses being assigned with /128  
  prefixes 
On Thu, 28 Sep 2017 20:03:48 +0200
"harald.albrecht" <harald.albrecht@xxxxxxx> wrote:

... So with dhcpcd you should never see an address/128. ...

Why not? An ISP could send a /128 address for the internet address of a perimeter router. That address would be the ISP's gateway address to hosts on the other side of the router. With Comcrash, I get a /128 every time in addition to the /60 I request. I then assign a different /64 from that /60 to each of the four IFs (including the internet IF). I can then use public addresses all around, and I can even use NAT for the /64 on the internet interface should internal hosts use private IPv6 addresses.