[Kea-users] kea-dhcp4 server in hybrid environment (dhcp-socket-type raw vs udp)

[Darren Ankney]

Hi Amano,

You can certainly answer both directly connected and relayed clients
simultaneously.  There is not enough information here to address any
specific problem that you have, but, you may have encountered one or
more of these pitfalls:

- You may have to specify the relay agent ip address in the subnet or
shared-network that should be selected for the client traffic
(https://kea.readthedocs.io/en/stable/arm/dhcp4-srv.html#local-and-relayed-traffic-in-shared-networks
and https://kea.readthedocs.io/en/stable/arm/dhcp4-srv.html#using-a-specific-relay-agent-for-a-subnet).
- You may have to specify the specific IP address for Kea to listen
upon (if you have more than one on the interface(s)) as it picks one
on it's own (https://kea.readthedocs.io/en/stable/arm/dhcp4-srv.html#interface-configuration)
which may not be the one you wanted.

There may be others but more information would be needed.  Please provide:
- Your configuration (redact any sensitive information such as
database passwords, of course).
- Logs of both types of clients.
- A PCAP obtained with `tcpdump -w <filename> port 67` containing both
types of clients would be quite helpful.

Thank you,
Darren Ankney

On Tue, Sep 8, 2026 at 6:50 AM Bogdan Veringioiu <bveringioiu at amano.eu> wrote:
>
> Hello,
>
> I have recently migrated isc-dhcp-server to kea-dhcp4 (debian trixie).
> After doing this I realized that I could not run kea the way I used to run isc, meaning:
> - Local clients (directly connected, same lan), this works fine with the default dhcp-socket-type = raw
> - Relayed clients (routed networks or clients connected over vpn tunnels) work fine with dhcp-socket-type = udp
> - Hybrid environments where kea should manage subnets with directly connected clients and routed subnets (relays) simply do not work. Kea needs to have either raw or udp for dhcp-socket-type.
>
> All 3 above scenarios used to work fine with isc with a single unified config. The way I understand it, scenario 3 is not possible with Kea.
> Can you please confirm this, or advise how can I use kea as a drop in replacement for isc ?
>
> I am working on a solution to run 2 kea instances, but it complicates things.
>
> Thank you very much
>
> --
> Bogdan Veringioiu
>
> Amano Parking Europe N.V.
> Uersfeld 24
> 52072 Aachen, Germany
>
> e-mail:   bveringioiu at amano.eu
> web:      www.amano.eu
>
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