Exploring virtual IPs
A virtual IP address can be used for a high-availability configuration, such as creating a Network Address Translation (NAT) in many different services on the same network port, or just for adding more than one IP address in the same network interface. In this section, we'll dive into each type of virtual IP that is supported by OPNsense and when to choose which virtual IP configuration type.
IP alias
An IP alias can be used as an additional IP address in a configured network interface. It will behave like the address configured in the interface, replying to ICMP requests (ping) and generating ARP packets on the network. The netmask must match with the network interface the IP alias will be created on; otherwise, you can set it as a single address (/32 CIDR for IPv4). You can even set an IP address from another network. There are some special cases, such as when the ISP delivers a small network (/30 CIDR) and you need to set up a high-availability installation...
