[systemd-devel] Prefix delegation and IPv6 subnetting

[Bent Bagger]

On 09/07/2022 23.11, Andrei Borzenkov wrote:
> Mailing list is not web forum where you can scroll up to read previous
> posts. On mailing list you are expected to include enough context from
> the previous message. Without going to archives and searching for your
> previous mail how should one know what Net0 etc means?
Point taken. I'll have your advice in mind in the future. I'm working on 
putting a post on my web page on what I did to get where I got. I'll 
post a notice here when I get it published.
>
> Having <PF> in one line and full prefix in another line does not help in
> understanding configuration. Is <PF> equal 2a06:4000:8073?
Yes. I had intended to anonymise the addresses but obviously failed 
miserably . Now you know everything about me 😉
>
> So you had to use external tool to implement prefix sub-delegation.
> Which just confirms that it is not possible with systemd-networkd.
I had hoped it was possible to do it using systemd-networkd only but 
having to realise that it can't be done is now part of 'lessons learned' 
from this exercise.
>> Now on to routing. Upstream routing is easy thanks to the default
>> routes, but how do I get the downstream routes established? The delegating router should add a route for the chosen prefix to the
>> requesting router, but can networkd do it or should I start looking at
>> routing protocols?
>>
> It is amazing how hard this is. See as example
>
> https://unix.stackexchange.com/questions/28106/dhcpv6-prefix-delegation-server-for-linux
>
> The suggested patch to ISC-DHCPD sounds good, but unfortunately it is
> not upstream.
>
> https://github.com/mpalmer/isc-dhcp/blob/mpalmer/client-address-data-expression/contrib/prefix-delegation-routing.rb
I discussed this with a routing knowable friend of mine earlier today 
and he suggested that OSPF6 might do the job. He sounded rather 
convincing so I'll give it a try. I might fail there too...

Bent