[Kea-users] How to get kea to reassign same IP after an explicit release (client reboot) if it has not been reused

[Nathan Neulinger]

Thanks. This is all I've been able to find as well.... Seems like such a hack - and not something that would work on any 
high traffic subnet unless the lease times were quite short to begin with.

Just seems like this should be a simple boolean flag "record any released lease as expired" to get it to feed into 
existing reclaim mechanism.

I saw a mail thread where "compliance with the protocol" was raised as a concern, but I don't see how the spec says 
"dhcp server MUST give a different address" or anything about how the dhcp server should pick between it's pools of 
addresses, that to me is purely a preference/ordering choice of the software. Actually ignoring/dropping DHCPRELEASE 
does seem like a protocol violation.

-- Nathan

------------------------------------------------------------------------------------------------------------------------
*From:* Blažej Krajňák [mailto:blazej.krajnak at gmail.com]
*Sent:* Saturday, October 8, 2022 at 4:03 AM
*To:* Nathan Neulinger <nneul at neulinger.org>
*Cc:* Kea-users at lists.isc.org <Kea-users at lists.isc.org>
*Subject:* [Kea-users] How to get kea to reassign same IP after an explicit release (client reboot) if it has not been 
reused

> Hi Nathan,
>
> I experienced the same strange behaviour. For me, the only solution
> was to prohibit "release" packets at all. In database I inserted:
>
> table: dhcp4_client_class
> {"id":"3","name":"DROP","test":"pkt4.msgtype==7","next_server":null,"server_hostname":null,"boot_file_name":null,"only_if_required":"0","valid_lifetime":null,"min_valid_lifetime":null,"max_valid_lifetime":null,"depend_on_known_directly":"0","follow_class_name":null,"modification_ts":"2022-05-17
> 20:18:42","user_context":null}
>
> table: dhcp6_client_class
> {"id":"2","name":"DROP","test":"pkt6.msgtype==8","only_if_required":"0","valid_lifetime":null,"min_valid_lifetime":null,"max_valid_lifetime":null,"depend_on_known_directly":"0","follow_class_name":null,"modification_ts":"2022-05-17
> 20:16:00","preferred_lifetime":null,"min_preferred_lifetime":null,"max_preferred_lifetime":null,"user_context":null}
>
>
> Blažej
>
> so 8. 10. 2022 o 5:45 Nathan Neulinger<nneul at neulinger.org>  napísal(a):
>>  From reading docs, it sure seems like these settings should result in the desired 'affinity' behavior, but it seems like maybe that is only working when it's an expiration, and not a 'release'?
>>
>>
>>      "expired-leases-processing": {
>>        "flush-reclaimed-timer-wait-time": 25,
>>        "hold-reclaimed-time": 3600,
>>        "max-reclaim-leases": 100,
>>        "max-reclaim-time": 250,
>>        "reclaim-timer-wait-time": 10,
>>        "unwarned-reclaim-cycles": 5
>>      },
>>
>>
>> ________________________________
>> From: Nathan Neulinger [mailto:nneul at neulinger.org]
>> Sent: Friday, October 7, 2022 at 10:41 PM
>> To:Kea-users at lists.isc.org  <Kea-users at lists.isc.org>
>> Subject: How to get kea to reassign same IP after an explicit release (client reboot) if it has not been reused
>>
>> Scenario:
>>
>>      Lightly used subnet, reasonably sized pool of addresses, served with an HA pair of Kea v2.2
>>      Client issues a RELEASE as part of reboot process
>>      Testing with v4 only at the moment
>>
>>
>> The client appears get a new IP from the pool every time it reboots. It does this even when no other leases have been granted to or even requested by other devices in the mean time.
>>
>> While this is certainly "valid" behavior - a client can't _expect_ to get the same IP, especially if network is busy/small pool/etc. -- it's not particularly user friendly. It's also not at all what users are used to on a network that was previously using an ISC DHCPd pair.
>>
>>
>> Is there any way to get Kea to hand out the same IP for a recently known client identifier if it has not already been given to another client? i.e. prioritize assignment of LRU priority on addresses in the pool unless it was the last client to be given a particular lease?
>>
>>
>> Ideal would be if the above could be time limited. Something like a "hold time" on a release - where it stays 'assigned but claimable if necessary' to a given client for some defined number of minutes after it is released.
>>
>>
>> Reservations are not what I'm looking for, we already have those, this is specifically in regards to 'purely dynamic pool' handling.
>>
>> -- Nathan
>>
>> ------------------------------------------------------------
>> Nathan Neulingernneul at neulinger.org
>> Neulinger Consulting                   (573) 612-1412
>>
>> --
>> ------------------------------------------------------------
>> Nathan Neulingernneul at neulinger.org
>> Neulinger Consulting                   (573) 612-1412
>>
>> --
>> ISC funds the development of this software with paid support subscriptions. Contact us athttps://www.isc.org/contact/  for more information.
>>
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-- 
------------------------------------------------------------
Nathan Neulingernneul at neulinger.org
Neulinger Consulting                   (573) 612-1412
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