Failover IP - Concepts
Failover IPs are IP addresses that you can order and move from one server to another (even across datacenters), without changing your whole configuration. If your server is out of order, you can move the failover IP to your fallback server, and have your services remain available without any downtime. Failover IPs can also be used as additional IP addresses for a single server, for example if you want to give each website in Plesk its own IP. Another functionality of Failover IPs is to create virtual machines on your Dedibox.
IP configuration refers to the assignment and management of IP addresses. Any server that needs to connect to the Internet or to another computer, needs an IP address. There are many ways to configure IP addresses, including the use of Failover IPs, Virtual MAC addresses, and the Reverse DNS of IPs.
A NAT-ed network is a mode of networking for virtual machines, another being bridged networks. In NAT mode, your server and its virtual machines are seen as one single server. As only the MAC address of your physical network card is broadcasted on the network, you do not require virtual MAC addresses for this network mode.
Reverse DNS, or rDNS, is exactly the opposite of classic forward DNS as we know it. Forward DNS maps a hostname to an IP address. Reverse DNS means we are mapping the IP address to a hostname. This can be very useful, especially if you want to send emails from your server.
Virtual MAC Address
Virtual MAC addresses are associated with Failover IPs, and are virtual versions of MAC addresses that identify physical hardware. Virtual MAC addresses allow you to create a bridged network of virtual machines from your server, where the physical server and its virtual machines are identified as different machines at the network level. The same virtual MAC can be associated with several Failover IPs.
Virtualization refers to the creation of one or multiple virtual machines on a physical server. This can be achieved via virtualization solutions such as VMware vSphere Hypervisor (ESXi) or Proxmox. Virtualization allows you to create separate environments for your different services (for example keeping mail and web services on different VMs) or to launch several virtual machines to make better use of the performance of the server. To communicate on the Internet, each of your virtual machines needs an IP Address. You can use Failover IPs for this purpose. If you want to create a bridged network for your virtual machines, you will also need to configure Virtual MAC addresses.