[Kea-users] KEA DHCP4 client classes with mysql

[Darren Ankney]

Hi James,

You will need a hosts_database that specifies mysql as shown here:
https://kea.readthedocs.io/en/kea-3.0.2/arm/dhcp4-srv.html#dhcpv4-hosts-database-configuration
something like this:

```
    "hosts-databases": [
      {
        "name": "kea",
        "password": "kea",
        "type": "mysql",
        "user": "kea"
      }
    ]
```
You will only need to load libdhcp_myslq.so, libdhcp_hosts_cmds.so,
for this specific purpose.  For a global host reservation, you need to
set "reservations-global": true as described here:
https://kea.readthedocs.io/en/kea-3.0.2/arm/dhcp4-srv.html#fine-tuning-dhcpv4-host-reservation

To add such a reservation (global) using host_cmds, you need to send
the reservation-add API command to Kea using subnet-id 0 as described
here: https://kea.readthedocs.io/en/kea-3.0.2/arm/hooks.html#the-reservation-add-command

Something like this:
```
{
    "command": "reservation-add",
    "arguments": {
        "reservation": {
            "subnet-id": 0,
            "hw-address": "1a:1b:1c:1d:1e:1f",
            "ip-ddress": "192.0.2.1",
            "client-classes": [ "classa" ]
        }
    }
}
```

After all of that, Kea should be able to find your reservation.

Thank you,
Darren Ankney


On Thu, Feb 5, 2026 at 8:05 AM James Jalbert via Kea-users
<kea-users at lists.isc.org> wrote:
>
> Hello, I hope this is the right list for this.....
>
> I am setting up the KEA DHCP4 server version 3.0.2 and trying to get client classes to work for my subnets. Here is what I have, and what has worked.
>
> I set up a global host reservation in the dhcp4.conf file. I set the host reservation with an ip address of one of my subnets and specify client_classes as the class name I want to use(we will say classa). In my subnet lists, I am setting a dynamic pool and telling the server, only give an address from this pool if the class = classa. With the client class set on the reservation, the machine gets an address, exactly what I want.
>
> Now I am trying to move the host reservation to mysql, as I have thousands of reservations. However, when I put "classa" under the dhcp4_client_classes it is not passed on to the server when the client requests its ip address. I get a message on the server that says failed to allocate address for client with classes ALL, Vendor_Class......., and UNKNOWN
>
> Why is the class not being sent from the database to the server?
> I have loaded the libdhcp_classes_cmds.so, libdhcp_myslq.so, libdhcp_hosts_cmds.so, libdhcp_subnet_cmds.so libraries. Anyone have any thoughts?
>
> Thanks for any help.
> James Jalbert
> Network Administrator
> Eastern Aroostook RSU #39
> Phone: 207-493-4246 Ext 1275
>
>
>
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