We run VM's in azure behind LB and public dedicated IP address. The customer requires proof of ownership of the dedicated IP address. Or if that's impossible, than he requires to have the ability to at least check to see if the IP address is eclusively provisioned to our VM's. When he checks the RIPE (IANA) register, he sees it is registered to Microsoft, and not to us. What is the best way to deal with this request?
The customer requires proof of ownership of the dedicated IP address.
Unless this customer is willing to pay an massive premium for you to really own an IP address block (more info...is this a multimillion dollar enterprise contract?) and pay for the talent and hardware to manage just that part of the job, what they are really asking for is a way to demonstrate that you have exclusive use of a single IP address.
Or if that's impossible, than he requires to have the ability to at least check to see if the IP address is exclusively provisioned to our VM's.
That's much easier to resolve, for example use this VirtualHost template for Apache and put a simple index.html page with a short message to the client on it:
<VirtualHost *:80> ServerName IP.AD.DR.ESS DocumentRoot /var/www/something DirectoryIndex index.html </VirtualHost>
Now they can visit the IP address directly and see proof that you control it.
I suspect that this customer does not have a good understanding of the situation, or your company is in way over it's head. Good luck resolving this matter either way. They probably copied some contract/legal boilerplate without really understanding what this would actually cost to deliver.