V2110 sending DHCP inform packets

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We have got a V2110 configured as cloud controller. It is fully functional with some 30 ap's connected to it.
It has one (outside) interface directly connected to the internet. On this interface some of the ap's connect to the controller with secure tunnel.

On this outside interface we see that the v2110 is sending dhcp inform packets.
In these packets it asks for the option 78 (parameter request list).

Any idea's why the controller is looking for (another) controller?

Kind regards,