From: Stefan Sperling <stsp@stsp.name>
Subject: Re: Use IPv6 /128 instead of /64 for PPP interfaces
To: Denis Fondras <denis@openbsd.org>
Cc: tech@openbsd.org
Date: Sun, 17 Nov 2024 11:48:11 +0100

On Sat, Nov 16, 2024 at 07:50:14PM +0100, Denis Fondras wrote:
> While working on IPv6 for pppd(8), I tried to use the EUI64 address as the PPP
> local address and failed because the kernel does not allow to change the netmask
> from /64 to /128.
> I propose we change the netmask for PPP interfaces to /128. Having a /64 is
> useless anyway on a PPP link.
> 
> (the alternative would be to generate another local address in pppd(8) but it
> seems overkill to me and we end up we 2 link-local addresses).
> 
> What do you think ?

Why do you need a /128? A /64 prefix should work, and you're probably
not going to be using other addresses from this range anywhere else.