[Kea-users] KEA DHCPv6 subnet prefixes from upstream IA_PD

[Darren Ankney]

Perhaps you could make use of the "include" mechanism?
https://kea.readthedocs.io/en/kea-2.7.5/arm/config.html#configuration-files-inclusion

On Tue, Jan 14, 2025 at 2:25 PM Owen DeLong <owen at delong.com> wrote:
>
> Is there any way to at least template the configuration so that I don’t have to change every occurrence of the prefix in the
> Entire file, but rather change a configuration variable that is referenced everywhere?
>
> I’m presuming some variant of the concat() expression commonly used in client classing might be useful here, but It’s not
> Clear to me how widely expressions can be used in a kea configuration file outside of client classes.
>
> If that capability doesn’t currently exist, it’s probably very much worth adding to the enhancements list.
>
> Owen
>
>
> > On Jan 14, 2025, at 10:02, Darren Ankney <darren.ankney at gmail.com> wrote:
> >
> > Hi Owen,
> >
> > I can't think of anyway from within Kea to do this.  Kea would have no
> > knowledge of what prefix was delegated.  I would say that you would
> > need to do scripts or find some consumer device that already does this
> > for you (e.g., perhaps one of the ASUS routers?).
> >
> > Thank you,
> > Darren Ankney
> >
> > On Tue, Jan 14, 2025 at 4:33 AM Owen DeLong via Kea-users
> > <kea-users at lists.isc.org> wrote:
> >>
> >> I’ve got a router running on a linux box using IPv4 NAT, and the KEA dhcp4 configuration is limited, but simple because my only option is to assign static RFC-1918 subnets and NAT them.
> >>
> >> However, for IPv6, I’m receiving an IA_PD and I’m able to use systemd-networkd to put the prefixes on the interfaces, but I’m stumped how to get KEA to pick up those prefixes to build DHCPv6 pools for address assignment. Sadly, I’ve got a few devices that won’t do SLAAC (yes, I know this is sacrilege, but I lack leverage to move the vendors in question). My clients that speak SLAAC are getting valid information and working.
> >>
> >> However, I’d like to provide M+O bits and do some reservations and stateful DHCPv6 in some cases. However, I don’t want to have to go in and edit the kea-dhcp6.conf every time the upstream decides to change the delegated prefix, so I’m trying to avoid hardcoding a dynamic prefix into the kea configuration file.
> >>
> >> Is there currently any way to do this in KEA? I suppose worst case, I can write scripts to update the kea configuration and put them in systemd-networkd hooks so that when the prefix is changed, they update kea, but that feels horribly hacky and I can’t help but think this would be a common implementation situation in the SOHO world.
> >>
> >> Any pointers or assistance greatly appreciated. If the question is asked and answered, links are appreciated as I haven’t found the answer in any of my searching so far.
> >>
> >> Thanks,
> >>
> >> Owen
> >>
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