Hello, This is due to precedence which is documented here: https://kea.readthedocs.io/en/kea-2.6.1/arm/dhcp4-srv.html#standard-dhcpv4-options
where it says: "The current Kea options precedence order is (from most important to least): host reservation, pool, subnet, shared network, class, global." Kea will use the first option content that it finds for a particular option in that above order. Note that subnet comes before class. You can use the flex_option to override option content based on class membership: https://kea.readthedocs.io/en/kea-2.6.1/arm/hooks.html#libdhcp-flex-option-so-flexible-option-actions-for-option-value-settings Thank you, Darren Ankney On Tue, Mar 4, 2025 at 11:08 AM Walter Reiner via Kea-users <kea-users@lists.isc.org> wrote: > > Hi, > > I'm trying to overwrite option-data fields, e.g. domain-name-servers but also > others, for specific reservations identified by MAC address. As the hosts are > not separable by different pools, I thought the best option would be to > create client-classes with the option-data I want to override and assign them > through reservations to the clients so I don't have to duplicate this > information through option-data blocks for every client. For clients without > a reservation the idea was to set default option-data values on the subnet > level. > > I have the following configuration: > > ~~~ > { > "Dhcp4": { > ... > "client-classes": [ > { > "name": "google-ns", > "option-data": [ > { "name": "domain-name-servers", "data": "8.8.8.8" } > ] > } > ], > "subnet4": [ > { > "id": 1, > "subnet": "192.168.24.0/24", > "pools": [ { "pool": "192.168.24.6 - 192.168.24.100" } ], > "option-data": [ > { "name": "routers", "data": "192.168.24.243" }, > { "name": "domain-name-servers", "data": "192.168.24.2" }, > ], > <?include "/etc/kea/reservations.json"?> > } > ], > ... > } > ~~~ > > Which includes the following reservations: > > ~~~ > "reservations": [ > { > "hw-address": "aa:bb:cc:dd:ee:ff", > "ip-address": "192.168.24.31", > "hostname": "dhtc01", > "client-classes": ["google-ns"] > }, > ] > ~~~ > > In this example, clients however always get the subnets domain-name-servers > option instead of the one configured in the assigned client-class. When I > explicitly add the option-data to the reservation, the overwrite works. > > I'm using isc-kea-dhcp4-server 2.6.1-isc20240725093407 on Debian 12. > > Any pointers are greatly appreciated. > > Thank you! > > -- > 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. > > Kea-users mailing list > Kea-users@lists.isc.org > https://lists.isc.org/mailman/listinfo/kea-users -- 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. Kea-users mailing list Kea-users@lists.isc.org https://lists.isc.org/mailman/listinfo/kea-users
