FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
This article provides the solution how to add a VIP entry without the error 'a duplicate entry already exists'.

1) A VIP name test has been created where external IP mapped to WAN1 and mapped to internal IP where UDP port-forwarding 10000 has been configured to map port 10000.

2) When a user is trying to create second object with VIP name new where external IP mapped to IP where TCP port forwarding done to 222 to 222 but when saving the VIP getting error 'a duplicate entry already exists'.

3) If the VIP with external IP address is mapped to same internal even though Port or protocol different the firewall will not allow to create the VIP entry as firewall will do IP lookup not the ports On VIP interface set the Interface to 'Any' or map the interface to the VIP entry to the WAN1.