[Kea-users] from isc dhcp classes -> kea 3.0

[Darren Ankney]

Hi Gregor,

You can safely use either one.  When Kea encounters a subnet/pool for
which 10.0.0.2 is not relevant, it will not assign the address.  The
client will instead receive a pool address.

Thank you,
Darren Ankney

On Mon, Nov 24, 2025 at 3:52 AM Gregor Kling <gregor.kling at its.thm.de> wrote:
>
> Hi Darren,
>
> On 11/21/25 4:38 PM, Darren Ankney wrote:
> > Hello Gregor,
> >
> >> Hi Darren,
> >>
> >> Deciding the reservation model
> >>
> >> 9.3.9. Global Reservations in DHCPv4 describes in general our
> >> setup. Clients generally can roam in our network based on the
> >> attributed "pool class" to the specific mac address and the
> >> "accessability" of the specific network.
> >>
> >> The following section:
> >>
> >> #+begin_quote 9.3.9. Global Reservations in DHCPv4:
> >> An address assigned via global host reservation must be feasible for the
> >> subnet the server selects for the client. In other words, the address
> >> must lie within the subnet; otherwise, it is ignored and the server will
> >> attempt to dynamically allocate an address. If the selected subnet
> >> belongs to a shared network, the server checks for feasibility against
> >> the subnet's siblings, selecting the first in-range subnet. If no such
> >> subnet exists, the server falls back to dynamically allocating the address.
> >> #+END_quote
> > This is generally true, but you are not (as far as I understood)
> > assigning an address to the clients in the reservation and instead are
> > selecting a pool for them to use for a dynamic address with the
> > reservation (by adding the client to one or more classes and using a
> > class guard on the pools).
>
> Generally true - yes - but with the following exception.
>
> Again given the following setup. When  the host with the
> mac "a1:bb:cc:dd:ee:ff" visits his "homebase",
>
> subnet id 1 it should be given the  "ip-address": "10.0.0.2" and not a
> pool address.
>
> Should this host however visit, for example subnet id 2, it should be
> given a pooladdress.
>
> So the the question remains (on this blurry monday morning) - which
> reservation model should i use?
>
> #+begin_quote
> {
> "Dhcp4": {
>          "client-classes": [{
>              "name": "pool_name_1",
>              "valid-lifetime": 3600
>          },
>          {
>              "name": "pool_name_etc",
>              "valid-lifetime": 3600
>          },
>          ],
>          "subnet4": [
>          {
>            "id": 1,
>            "subnet": "10.0.0.0/24",
>            "pools": [
>                          {
>                            "pool": "10.0.0.10-10.0.0.100",
>                            "client-classes": ["pool_name_1",
> "pool_name_etc"]
>                          }
>            ],
>            "reservations": [
>            {
>                "hw-address": "a1:bb:cc:dd:ee:ff",
>                "ip-address": "10.0.0.2",
>                "client-classes": [ "pool_name_1", "pool_name_etc" ]
>
>            },
>            {
>                "hw-address": "a2:bb:cc:dd:ee:ff",
>                "ip-address": "10.0.0.3",
>                "client-classes": [ "pool_name_etc" ]
>
>            }
>
>          ]
>        },
>        {
>          "id": 2,
>          "subnet": "192.0.3.0/24",
>          "pools": [
>              {
>                  "pool": "192.0.3.10-192.0.3.20",
>                  "client-classes": [ "pool_name_1" ]
>              },
>          ],
>           "reservations": [
>            {
>                "hw-address": "a1:bb:cc:dd:ee:ff",
>                "client-classes": [ "pool_name_1", "pool_name_etc" ]
>
>            },
>            {
>                "hw-address": "a2:bb:cc:dd:ee:ff",
>                "client-classes": [ "pool_name_etc" ]
>
>            }
>
>          ]
>
>      }
> ]
>
> }
>
> }
>
> #+end_quote
>
>
> --
>
> Gregor Kling
>
> Abteilung ITS, Sachgebiet ITS-N
> Technische Hochschule Mittelhessen
> University of Applied Sciences
> Tel: 0641/309-1292
> E-Mail: gregor.kling at its.thm.de
>
> --
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