Another Way, if @Sebastian confirm i could try to test some tricky thing like adding GATEWAYDEV to interface config in order to route all traffic to eth instead of default IP.
If it will work, we should add new entry GATEWAYDEV in DB and on WEB UI.
I’m not sure I understand the request, does OVH force servers to receive IP only in dhcp? So you can’t make the first webui access without this configuration?
Yes, you are completely right after successful installation over CentOS you could not log in or even ping, because of the interface is not properly configured.
That was the root of the issue.
Thus, we need some workarounds or fixes, because all our Newcomers will face with this 
It’s not enough.
Without reading the code, these are the first problems about using dynamic IP on green interfaces (and I bet I miss many others):
- code for trusted network will be broken
- shorewall rules must be rewritten using special macros, something like:
ETH0_IP=$(find_first_interface_address eth0) - the code of dhclient event hooks must be completely rewritten
- green/red zones on system with a single interface (like VPS) will not work
This can be done.