[Kea-users] DHCP4 reservation by DNS hostname lookup - how?

[Darren Ankney]

Hello Jeff,

I have been informed privately by someone on the Kea development team
who also worked on ISC DHCP in the past that I am incorrect here.  ISC
DHCP dynamically resolved FQDNs and did in fact manage multiple
answers.  Sorry for the misinformation!

Thank you,
Darren Ankney

On Thu, Oct 10, 2024 at 6:22 AM Darren Ankney <darren.ankney at gmail.com> wrote:
>
> Hi Jeff,
>
> Please be aware that ISC DHCP only looked up these DNS entries when
> the process started.  So if you ran the ISC DHCP process for many
> months, the notion that ISC DHCP had of these endpoint IP addresses
> would diverge from what was currently in DNS if there were changes.
> It was misleading to users such as yourself who thought that lookups
> were ongoing when they were not.
>
> Thank you,
> Darren Ankney
>
> On Thu, Oct 10, 2024 at 3:26 AM Jeff Armstrong <jeff at whitefern.com> wrote:
> >
> > Isn't this a major loss of functionality? Is there a plan / ticket to add this core feature?
> >
> > Manually maintaining IP reservations in multiple places (DNS, Reverse DNS and DHCP) is a pita that is prone to error.
> >
> > Decisions on IP range allocation fit more naturally in DNS as pre-release testing there can confirm that both forward and reverse IP allocation is consistent.
> >
> > Surely you don't expect DevOps to maintain forward IP allocation in DHCP and reverse allocation in DNS?
> >
> > Regards,
> >
> > Jeff
> >
> > On 09/10/2024 17:01, Peter Davies wrote:
> >
> > Hi Jeff,
> >    You cannot use a fqdn in place of an address within a host reservation in Kea.
> >
> > Kind Regards Peter
> >
> > ________________________________
> > From: "Jeff Armstrong" <jeff at whitefern.com>
> > To: "Kea-users at lists.isc.org" <kea-users at lists.isc.org>
> > Sent: Wednesday, 9 October, 2024 17:10:39
> > Subject: [Kea-users] DHCP4 reservation by DNS hostname lookup - how?
> >
> > In the isc-dhcp-server I could use DNS to make reservations:
> >
> > host gh-ja-iphone-uk { hardware ethernet 5b:c7:43:37:a2:b0; fixed-address ja-iphone-uk.gh.mydomain.com; }
> > and the IP assigned would be retrieved from DNS.
> >
> > In Kea I have tried:
> >
> >     "reservations": [
> >       { "hw-address": "5b:c7:43:37:a2:b0", "fixed-address": "ja-iphone-uk.gh.mydomain.com" }
> >     ]
> >     "reservations": [
> >       { "hw-address": "5b:c7:43:37:a2:b0", "ip-address": "ja-iphone-uk.gh.mydomain.com" }
> >     ]
> >     "reservations": [
> >       { "hw-address": "5b:c7:43:37:a2:b0", "host-name": "ja-iphone-uk.gh.mydomain.com" }
> >     ]</ div>
> > but these don't work - the first two stop the server from starting with a configuration error, and the third just assigns from the pool.
> > I have read https://kea.readthedocs.io/en/kea-2.6.1/arm/dhcp4-srv.html#host-reservations-in-dhcpv4 - but cannot find a clear list of all the recognised options for reservations.
> > Help?!?
> > Many thanks,
> > Jeff
> >
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