my ISP
delivers a physical network port with a non-routable ip 10.0.0.5 (for example)
and the server of this ISP does not have authentication it validates the ip of origin.
today the client has a Vitalpbx running locally where I configured this private network on eth2 and created the routes (everything working ok)
but the customer wants to take his pbx to the cloud for other reasons, but he doesn’t want to change his ISP.