You can authorize operating system installations with the help of a datacenter management software such as DCIManager, which allows the client to log in and install the system. Exploitation of his choice. You can also use it to manage the servers yourself. Customers can also install the operating system using IPMI with the attached ISO of their choice but sometimes slow and difficult to use.
You can create an access list so that the switch port of a particular dedicated server only allows the traffic for the assigned IP addresses. Another option is to use a private VLAN to avoid any communication between different switch ports.