If you have a hardware firewall installed, you can manage the mappings between internal and external IP addresses. Internal IP addresses are used by your server and are not visible to the outside world. External IP addresses are those used to access your server from the outside. Your hardware firewall must be configured to pass traffic from an external IP address to the correct internal IP address.
IP address allocation is monitored. Attempting to add IP addresses to your server that have not been purchased is a violation of your terms of service agreement and may result in the suspension of your account.