How to use openstack compute resources (with flat network)?

Hi,

Foreman 1.14.3 here.

I'm trying to understand how to use foreman with openstack compute resources… and I sort of fail… or at least with a flat network.
I was able to connect foreman to openstack. I was able to link OS images and to associate user templates to OSes

I then tried creating a VM, and I specified an IP since I selected the flat network.

Foreman then created the host in openstack, rendered the user templates, and things started failing after that : foreman allocated another completely different IP from openstack… ?
OK, let's say I can work with this (I can't : I'm not allowed to manage the DNS using anything, I have to start a VPN and use obscure tools to manage the DNS IPs) : since I selected a cloud-init ready image (CentOS 7), I would assume that the VM would use that cloud-init, but I'm failing at understanding how that works with foreman …

The VM is failing at finding anything, checking in openstack, it only has one volume attached (I read in the foreman 1.9 doc that a small volume was attached for the cloud-init config, but it's not for me)

Since I'm trying a deploy a VM on a flat network, I disabled openstack's dhcp on that network so that foreman's dhcp could be used and so that there's no conflict, but I don't see any DHCPd lease for the VM on the foreman server.
And actually, I don't find a MAC address for the VM neither in foreman nor in the openstack created host…

Anyone would have knowledge/hints for openstack usage with foreman ?

Note : I successfully kicked a cirros instance on that network, gave it an IP, and was able to reach my network : I therefore know the flat network is working…

Thanks