UTM interface to connect to on-the-premises router (behind the firewall) with a WAN IP - Management, Networking, Logging and Reporting - UTM Firewall - Sophos Community
Mikrotik with Multiple WAN IP's and Port Forwarding / HAIRPIN NAT | Syed Jahanzaib - Personal Blog to Share Knowledge !
SOLVED] How to configure each port with public static IP on switch/router? - Networking
Assigning IP address to interface from routed subnet | Ubiquiti Community