Technical Tip: FortiGate can create max 32 secondary IP address per interface.

[ChrisTan]

Description	This article describes that FortiGate can only allow a maximum of 32 secondary IP addresses per interface.
Scope	FortiGate.
Solution	Sometimes, FortiGate needs to apply multiple secondary IP addresses, especially in the cloud environment. A maximum of 32 secondary IP addresses can be created for each interface. The message 'Command fail. Return code -4 (reached the maximum number of entries)' will appear if more than 32 are added. Enable port forwarding if there are more than 32 internal IP addresses to map. Note: The maximum number of secondary IPs on each interface has been extended to 256 on FOS v7.2.4 and later versions. Refer to the following page for more details: Maximum Values Table