[Kea-users] Intermittent "Address already in use" Error When Creating DHCP Reservations (Micetro 25.2.1, Kea 2.6.4)

[Darren Ankney]

Hi Tom,

This sounds like you may have the HA hook and the kea-ctrl-agent
attempting to use the same IP/port combo.  This creates a race
condition where sometimes kea-dhcp4 or kea-dhcp6 wins and sometimes
kea-ctrl-agent wins.  This assumes you have the parameters
"enable-multi-threading" and "http-dedicated-listener" set true (which
is the default in 2.6.x). Confirm that your IP address / port
specified in your kea-ctrl-agent configuration do not match the "url"
specified in the HA configuration for each peer in that case.

More information:
https://kea.readthedocs.io/en/kea-2.6.4/arm/hooks.html#multi-threaded-configuration-ha-mt

Thank you,
Darren Ankney

On Fri, Jul 10, 2026 at 4:01 AM Zenz, Thomas via Kea-users
<kea-users at lists.isc.org> wrote:
>
> Dear ISC KEA Community,
>
> We’re encountering an intermittent issue when creating DHCP reservations in our Micetro environment (version 25.2.1) running on Kea (2.6.4) in a high-availability (HA) setup.
>
> The same request succeeds at times but fails unpredictably with the following server response:
>
>
>
> {'error': {'code': 5376, 'message': 'Error creating a reservation: Unable to update the configuration due to an error: Error initializing hooks: CmdHttpListener::run failed: unable to setup TCP acceptor for listening to the incoming HTTP requests: bind: Address already in use.'}}
>
>
>
> The HTTP response code is 400 (Bad Request), which is misleading since the request itself is valid (identical requests succeed at other times).
>
>
>
> Additional observations:
>
> During the failure, the primary server appears to be in standby mode (as if it were the secondary).
> The only workaround we’ve found is manually running keactrl reload on the primary server to restore normal operation.
>
> Our logs suggest the issue stems from a resource conflict (e.g., TCP port exhaustion or a lingering listener), but we’re unsure how to diagnose or resolve it.
>
> Has anyone encountered this behavior before? Any insights or troubleshooting steps would be greatly appreciated.
>
> Thank you in advance!
>
>
>
> Tom
>
>
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