[Kea-users] a few questions from a Kea newbie

[Jason Keltz]

Hi Kevin,

Thanks for your message!  It was very helpful.

I just tried to do host reservation with memfile and indeed it mostly worked.

Multiple ether mapped to same IP is working as you said (with the understanding that one would have to released first).

However, my experience with multiple IPv4 addresses to the same ether does not work, and you said that it should.

I tried to reserve:
hw-address: 78:24:af:45:32:99 with hostname test1 and ip <masked ip>
hw-address: as-above with hostname test1 and different ip

When running kea, it loads the first reservation, but after reading the second one, it reports that this HW address has already been added so it can't be added again - thoughts?:

DHCP4_PARSER_FAIL failed to create or run parser for configuration element reservations: failed to add new host using the HW address '78:24:af:45:32:99' to the IPv4 subnet id '0' as this host has already been added
DHCP4_CONFIG_LOAD_FAIL configuration error using file: /xconf/kea/kea-dhcp4.conf.fowl1, reason: failed to add new host using the HW address '78:24:af:45:32:99' to the IPv4 subnet id '0' as this host has already been added
DHCP4_INIT_FAIL failed to initialize Kea server: configuration error using file '/xconf/kea/kea-dhcp4.conf.fowl1': failed to add new host using the HW address '78:24:af:45:32:99' to the IPv4 subnet id '0' as this host has already been added

Jason.
________________________________
From: Kea-users <kea-users-bounces at lists.isc.org> on behalf of Kevin P. Fleming <lists.kea-users at kevin.km6g.us>
Sent: Monday, November 13, 2023 8:07 PM
To: kea-users at lists.isc.org <kea-users at lists.isc.org>
Subject: Re: [Kea-users] a few questions from a Kea newbie

1) No, it is not necessary to use a database in order to use reservations.

2) Unfortunately this is not currently possible unless you can ensure that the host releases its lease before switching interfaces. I have discussed this in a number of threads on this list and there is an open issue for it.

3) Yes you can have multiple reservations for the same hardware address.

On Mon, Nov 13, 2023, at 16:50, Jason Keltz wrote:
> Hi.
>
> I'm investigating migrating from ISC DHCPd to Kea and running into a few
> issues.
>
> I see some conflicting information online, due to kea development over
> time, so I was hoping to ask here for some clarification.
>
> 1) Is it really necessary to install a database backend such as
> Postgres/MySQL if I want to have static host reservations?  This was
> working so perfectly with dhcpd without any db backend for such a long
> time.  Not having a DB backend on the DHCP server means one less thing
> to worry about when Kea is updated, or the DB updated.   I accept that
> performance of the DB is likely going to be better than the reservations
> being stored in a text file, but for my basic setup, it just doesn't
> matter to me. The simplicity of not needing a DB for this over-rides the
> performance gain that may be attained with a DB.  I just want to be sure
> that I haven't overlooked something.
>
> 2) Does Kea permit multiple ethernet addresses mapped to the same IPv4
> IP?  I do this for multiple reasons - for example, I may have a server
> that has 2 ethernet addresses, and when I plug it in, whether I use one
> or the other network port, the IP should be the same.  Obviously I
> shouldn't plug in both or things would break, but that would be my
> problem.  At the same time, maybe a laptop has an ethernet port built
> in, but when plugged into a dock that has its own network port, I want
> the machine to get the same IP one way or the other (static
> reservation).  Now, I think I can permit this by enabling
> "ip-reservations-unique" to false, but I wanted to clarify.  Again, I
> did this with DHCPd all the time.
>
> 3) Finally - does Kea permit multiple IPv4 IPs for the same ethernet
> address?  I believe that "ip-reservations-unique" does not permit this,
> yet this is more important for me, and I did this with dhcpd.  For
> example, in different places in the building there are different VLANs.
> Most hosts just get a static IP reservation from DHCP.  99% of hosts
> will ever be on one VLAN. However, for say, my test laptop that has a
> single IP reserved on every VLAN - can Kea handle this scenario?
>
> Answers to these questions would be a great start!
>
> Thanks for reading..
>
> Jason.
>
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