LACP on Fortigate

Link Aggregation Control Protocol (LACP)

To create a link aggregation interface in the GUI:
  1. Go to Network > Interfaces.
  2. Click Create New > Interface.
  3. Set Type to 802.3ad Aggregate.
  4. Configure the other settings as required.
  5. Click OK.
To create a link aggregation interface in the CLI:
configure system interface 
  edit "aggregateinterf"
    set vdom "root"
    set type aggregate
    set member "internal1" "internal2"
    set device-identification enable
    set lldp-transmission enable
    set role lan
    set snmp-index 13
  next
end
To check the aggregate interface status:
diagnose netlink aggregate name <name of aggregate interface>

source: https://docs.fortinet.com/document/fortigate/6.2.0/new-features/226063/lacp-support-on-entry-level-e-series-devices-6-2-1