Since you cannot currently assign multiple public IP addresses to a system in the virtual data center (vDC), you have to use a little trick here.
First you have to get an additional IP address in the vDC in the IP manager.
Then switch on the failover function for this IP address.
After that you can click on “Firewall> Virtual IPs”.
“IP Alias” is selected as the type. Then you enter the IP address you obtained earlier, and indicate that it is on a /24 network.
This IP address is now available for NAT and other pfSense functions.