Hi Ben, At this point, looking at logs would be the way forward. As I said previously, Kea should not be offering a different address unless the previous address was in use. if you set "severity": "DEBUG", and "debuglevel": 99 in your "loggers" section, then Kea will print details about the address selection process to "/var/log/kea/kea-dhcp4.log". This may not completely answer the question but might. If this is a busy production server, you may not want to do this, however.
Thank you, Darren Ankney On Tue, Nov 4, 2025 at 6:23 PM Ben Bridges <[email protected]> wrote: > > Hi Darren, > > There is only one client in this subnet. There are no other DISCOVERs coming > from any other devices. If Kea is expected to keep offering 10.255.237.201 > to clients until a client completes a DORA for the address, why is Kea > offering different IP addresses to this one client? (This behavior appears > to be different than ISC's older DHCP server.) > > Thanks, > .Ben Bridges. > > -----Original Message----- > From: Kea-users <[email protected]> On Behalf Of Darren Ankney > Sent: Saturday, November 1, 2025 1:28 PM > To: Kea user's list <[email protected]> > Subject: Re: [Kea-users] Kea offering multiple different IP addresses to same > client > > Hi Ben, > > It looks like you are accepting all of the defaults. The allocator > will be "iterative". That matches with the ip addresses counting up > in your offers. I am not sure if this will prevent the behavior you > are seeing, but try setting "offer-lifetime": 60, in your subnet (see > here: > https://kea.readthedocs.io/en/kea-2.6.4/arm/dhcp4-srv.html#temporary-allocation-on-dhcpdiscover). > This parameter might cause Kea to persistently offer this same address > to this same client. > > Kea should be offering the next IP address that is available. I > assume other clients are not being allocated the address that was > previously offered in between DISCOVERS from this client? Otherwise, > if no client is using 10.255.237.201 then each client that sends a > discover should be offered this same address until someone completes > the DORA for the address. > > Thank you, > Darren Ankney > > On Mon, Oct 27, 2025 at 8:12 PM Ben Bridges <[email protected]> wrote: > > > > Hi Darren, > > > > Thanks for responding. Below is the configuration: > > > > { > > "Dhcp4": { > > "interfaces-config": { > > "interfaces": [ "ens3" ] > > }, > > > > "control-socket": { > > "socket-type": "unix", > > "socket-name": "kea4-ctrl-socket" > > }, > > > > "lease-database": { > > "type": "memfile", > > "lfc-interval": 3600 > > }, > > > > "expired-leases-processing": { > > "reclaim-timer-wait-time": 10, > > "flush-reclaimed-timer-wait-time": 25, > > "hold-reclaimed-time": 3600, > > "max-reclaim-leases": 100, > > "max-reclaim-time": 250, > > "unwarned-reclaim-cycles": 5 > > }, > > > > "valid-lifetime": 7200, > > > > "option-data": [ > > { > > "name": "domain-name-servers", > > "data": "10.1.1.1, 10.2.1.1" > > }, > > { > > "name": "tftp-server-name", > > "data": "10.2.1.9" > > }, > > { > > "name": "boot-file-name", > > "data": "boot.file" > > }, > > ], > > > > "client-classes": [ > > { > > "name": "Test-Clients", > > "test": "substring(option[60].hex,0,13) == '<redacted>'", > > } > > ], > > > > "hooks-libraries": [ > > { > > "library": > > "/usr/lib/x86_64-linux-gnu/kea/hooks/libdhcp_lease_cmds.so", > > }, > > ], > > > > "subnet4": [ > > { > > "id": 50, > > "subnet": "10.255.237.0/24", > > "pools": [ { "pool": "10.255.237.201 - 10.255.237.210", > > "client-class": "Test-Clients"} ], > > "option-data": [ > > { > > "name": "routers", > > "data": "10.255.237.1" > > } > > ] > > } > > ], > > > > "loggers": [ > > { > > "name": "kea-dhcp4", > > "output-options": [ > > { > > "output": "/var/log/kea/kea-dhcp4.log", > > "maxver": 8 > > } > > ], > > "severity": "INFO", > > "debuglevel": 0 > > } > > ] > > } > > } > > > > Thanks, > > .Ben Bridges. > > > > -----Original Message----- > > From: Kea-users <[email protected]> On Behalf Of Darren Ankney > > Sent: Sunday, October 26, 2025 4:27 AM > > To: Kea user's list <[email protected]> > > Subject: Re: [Kea-users] Kea offering multiple different IP addresses to > > same client > > > > 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] > > -- > > 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] > -- > 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. 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