Override FortiGate block-intra vlan traffic

Sorry. I pasted a wrong link.
https://docs.fortinet.com/document/fortiswitch/7.4.5/fortilink-guide/801169/blocking-intra-vlan-traffic

The NOTE is below but basically the same with what @AEK said.

When intra-VLAN traffic blocking is enabled, to allow traffic between hosts, you need to configure the proxy ARP with the config system proxy-arp CLI command and configure a firewall policy. For example:

config system proxy-arp

edit 1

set interface "V100"

set ip 1.1.1.1

set end-ip 1.1.1.200

next

end

config firewall policy

edit 4

set name "Allow intra-VLAN traffic"

set srcintf "V100"

set dstintf "V100"

set srcaddr "all"

set dstaddr "all"

set action accept

set schedule "always"

set service "ALL"

next

end