[Kea-users] Kea offering multiple different IP addresses to same client

[Ben Bridges]

Greetings.

My apologies if this has been asked and answered before.  I did not find a thread on this subject in the archives of this list, but it seems like the sort of thing that might have been asked before.

We have some devices which prefer to receive DHCP offers from the DHCP server made by the same manufacturer as the clients.  They ignore the first four offers made by other DHCP servers and then finally accept/request the fifth offer.  When the DHCP DISCOVER packets from one of these devices are relayed to a Kea 2.6 server, Kea offers the device a different IP address in response to each of the five DISCOVER packets.  Is this by design?  The DISCOVER packets all appear to be identical except for the Transaction ID and Seconds Elapsed.  Why isn't Kea offering the same IP address to the client every time?  This is a test situation with only one device in the subnet, so there are no DHCP packets from any other devices.  "offer-lifetime" is not configured for the subnet and hence should be 0, but it seems to me that the purpose of the "offer-lifetime" parameter is probably to be able to offer the same IP address to a device sending multiple requests in the presence of requests from other devices.  There are no other requests in this case.

Below are the logs showing the receipt of the DISCOVER packets and the subsequent offers by Kea:

2025-10-14 08:05:54.776 INFO  [kea-dhcp4.packets/659.140495010055744] DHCP4_PACKET_RECEIVED [hwtype=1 xx:xx:xx:39:09:b5], cid=[01:xx:xx:xx:39:09:b5], tid=0x67458b6b: DHCPDISCOVER (type 1) received from 10.255.237.1 to <redacted> on interface ens3
2025-10-14 08:05:54.777 INFO  [kea-dhcp4.leases/659.140495010055744] DHCP4_LEASE_OFFER [hwtype=1 xx:xx:xx:39:09:b5], cid=[01:xx:xx:xx:39:09:b5], tid=0x67458b6b: lease 10.255.237.201 will be offered
2025-10-14 08:05:58.820 INFO  [kea-dhcp4.packets/659.140495018448448] DHCP4_PACKET_RECEIVED [hwtype=1 xx:xx:xx:39:09:b5], cid=[01:xx:xx:xx:39:09:b5], tid=0xc6237b32: DHCPDISCOVER (type 1) received from 10.255.237.1 to <redacted> on interface ens3
2025-10-14 08:05:58.820 INFO  [kea-dhcp4.leases/659.140495018448448] DHCP4_LEASE_OFFER [hwtype=1 xx:xx:xx:39:09:b5], cid=[01:xx:xx:xx:39:09:b5], tid=0xc6237b32: lease 10.255.237.202 will be offered
2025-10-14 08:06:06.776 INFO  [kea-dhcp4.packets/659.140495010055744] DHCP4_PACKET_RECEIVED [hwtype=1 xx:xx:xx:39:09:b5], cid=[01:xx:xx:xx:39:09:b5], tid=0x69983c64: DHCPDISCOVER (type 1) received from 10.255.237.1 to <redacted> on interface ens3
2025-10-14 08:06:06.776 INFO  [kea-dhcp4.leases/659.140495010055744] DHCP4_LEASE_OFFER [hwtype=1 xx:xx:xx:39:09:b5], cid=[01:xx:xx:xx:39:09:b5], tid=0x69983c64: lease 10.255.237.203 will be offered
2025-10-14 08:06:14.781 INFO  [kea-dhcp4.packets/659.140495018448448] DHCP4_PACKET_RECEIVED [hwtype=1 xx:xx:xx:39:09:b5], cid=[01:xx:xx:xx:39:09:b5], tid=0x73483366: DHCPDISCOVER (type 1) received from 10.255.237.1 to <redacted> on interface ens3
2025-10-14 08:06:14.781 INFO  [kea-dhcp4.leases/659.140495018448448] DHCP4_LEASE_OFFER [hwtype=1 xx:xx:xx:39:09:b5], cid=[01:xx:xx:xx:39:09:b5], tid=0x73483366: lease 10.255.237.204 will be offered
2025-10-14 08:06:22.784 INFO  [kea-dhcp4.packets/659.140495010055744] DHCP4_PACKET_RECEIVED [hwtype=1 xx:xx:xx:39:09:b5], cid=[01:xx:xx:xx:39:09:b5], tid=0x51dcb074: DHCPDISCOVER (type 1) received from 10.255.237.1 to <redacted> on interface ens3
2025-10-14 08:06:22.784 INFO  [kea-dhcp4.leases/659.140495010055744] DHCP4_LEASE_OFFER [hwtype=1 xx:xx:xx:39:09:b5], cid=[01:xx:xx:xx:39:09:b5], tid=0x51dcb074: lease 10.255.237.205 will be offered
2025-10-14 08:06:25.733 INFO  [kea-dhcp4.packets/659.140495018448448] DHCP4_PACKET_RECEIVED [hwtype=1 xx:xx:xx:39:09:b5], cid=[01:xx:xx:xx:39:09:b5], tid=0x51dcb074: DHCPREQUEST (type 3) received from 10.255.237.1 to <redacted> on interface ens3
2025-10-14 08:06:25.733 INFO  [kea-dhcp4.leases/659.140495018448448] DHCP4_LEASE_ALLOC [hwtype=1 xx:xx:xx:39:09:b5], cid=[01:xx:xx:xx:39:09:b5], tid=0x51dcb074: lease 10.255.237.205 has been allocated for 7200 seconds

I redacted part of each of the Client Identifiers, but they are all identical (as are the hardware addresses).

Thanks,
.Ben Bridges.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.isc.org/pipermail/kea-users/attachments/20251018/a6560b4c/attachment-0001.htm>