Hi Ben, It is not possible to answer this question without seeing your configuration. Generally speaking, the chosen lease allocator should have the most influence regarding what IP address is offered. See here: https://kea.readthedocs.io/en/kea-3.0.1/arm/dhcp4-srv.html#allocators-comparison of course offer lifetime (as you mention) could have some influence as well: https://kea.readthedocs.io/en/kea-3.0.1/arm/dhcp4-srv.html#temporary-allocation-on-dhcpdiscover
Thank you, Darren Ankney On Fri, Oct 17, 2025 at 8:13 PM Ben Bridges <[email protected]> wrote: > > 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. > > -- > ISC funds the development of this software with paid support subscriptions. > Contact us at https://www.isc.org/contact/ for more information. > > To unsubscribe visit https://lists.isc.org/mailman/listinfo/kea-users. > [email protected] -- ISC funds the development of this software with paid support subscriptions. Contact us at https://www.isc.org/contact/ for more information. To unsubscribe visit https://lists.isc.org/mailman/listinfo/kea-users. [email protected]
