[Kea-users] Lease affinity of released leases

Wed Nov 10 14:17:36 UTC 2021

Thanks a lot, Mattias!

That does answer my question. I guess for now I will have to mitigate the
issue in any of the ways I listed in the original post, and when I get the
time I might very well write a hook. It's about time I take up my C++
skills :-)

Den ons 10 nov. 2021 kl 15:05 skrev Mattias Johansson <
Mattias.Johansson at varnamoenergi.se>:

> Hi,
>
>
>
> I found this
>
>
>
> [Kea-users] Enable lease affinity with MySQL backend (isc.org)
> <https://lists.isc.org/pipermail/kea-users/2018-September/001997.html>
>
>
>
> ”Kea has a built in support for keeping an expired lease around for a
>
> configurable amount of time, which is driven by
>
> "expired-leases-processing" parameters described in the Kea User's
>
> Guide. In other words, if the lease expires (client does not renew the
>
> lease), the server won't remove this lease from the database
>
> immediately, but will rather wait a configured amount of time before it
>
> removes it. This doesn't preclude other clients from getting the lease
>
> if they request it, but in most cases the expired lease will simply be
>
> re-assigned to the client who had been using it before.
>
>
>
> Having said that, this doesn't work for cases when the client sends a
>
> Release to indicate that it stops using the lease. In such cases, the
>
> lease is removed from the database upon receiving the Release. There are
>
> no configuration knobs to keep the lease in the database for the client
>
> after the client releases the lease.
>
>
>
> The only possibility I see to address your use case at the moment is to
>
> write a simple hooks library which drops the received Release packets.
>
> The server won't process them and the leases will be left to expire in
>
> the database. When the client reboots it should get the same lease. That
>
> involves C++ coding though.”
>
>
>
>
>
> sounds like what you’re experiencing.
>
>
>
>
>
>
>
>
>
> *Från:* Kea-users <kea-users-bounces at lists.isc.org> * För *
> egor.grijuc at orange.com
> *Skickat:* den 10 november 2021 14:52
> *Till:* Johannes Midgren <johannes at midgren.net>; kea-users at lists.isc.org
> *Ämne:* Re: [Kea-users] Lease affinity of released leases
>
>
>
> Maybe a host reservation is a solution?
>
>
>
> *From:* Kea-users <kea-users-bounces at lists.isc.org> *On Behalf Of *Johannes
> Midgren
> *Sent:* Wednesday, 10 November 2021 15:47
> *To:* kea-users at lists.isc.org
> *Subject:* [Kea-users] Lease affinity of released leases
>
>
>
> TLDR: How do I make KEA offer the same IP to a host that is rebooted and
> that releases its IP address while shutting down?
>
>
>
> I have recently started to use KEA on my home network. I love the fact
> that I can control its configuration through Ansible and all the
> possibilities the REST API gives, so I'm very glad that I found the project!
>
>
>
> One thing that I still have not been able to get the way I prefer it
> though, is to have lease affinity in all cases. That is, I would like for a
> client to always get the same IP address when it reconnects (as long as
> it's still available of course). I have read the chapter about Lease
> Expiration (and Affinity) in the manual and I'm not sure the case I'm
> looking for is covered. The manual talks about expired leases, but I would
> like to have affinity also in the case that the lease has been released
> rather than expired. Using a packet sniffer I can see that clients tend to
> properly release the DHCP lease when being rebooted and when it gets online
> again it does a DHCP Discover and is offered a new IP address by the KEA
> DHCP4 server.
>
>
>
> Does anyone know if KEA is supposed to (or rather can be made to) work the
> way I intend it to or if lease affinity by design is only supposed to work
> for expired, thus not released, leases? (Or maybe something is wrong with
> my setup and this should actually work?)
>
>
>
> The problem I have is that cached DNS entries make hosts unavailable for
> some time after they are restarted - they are "sought for" by their old IP.
> I guess I can mitigate the issue by setting a very low TTL in my DNS
> configuration, but I would prefer to let KEA hold leases for a long time
> and reuse them instead. Another way would of course be to make reservations
> for all hosts where this matters, but that prevents the automation that I
> try to use KEA for.
>
>
>
> I have been playing with the expired-leases-processing configuration for
> the DHCP4 server, and I currently have this:
>
>
>
>        "expired-leases-processing": {
>            "flush-reclaimed-timer-wait-time": 300,
>            "hold-reclaimed-time": 604800,
>            "max-reclaim-leases": 100,
>            "max-reclaim-time": 250,
>            "reclaim-timer-wait-time": 180,
>            "unwarned-reclaim-cycles": 5
>        },
>
> I'm running KEA 1.8 (installed from CloudSmith repos) on CentOS Stream 8.
> I use the memfile lease-database, have DHCP-DDNS setup and I use the HA
> hook (with one primary, one standby and one backup host).
>
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