What command tests bandwidth on a FortiGate?

The diagnose traffictest command. It uses the FortiGate’s built-in iperf3 client to measure throughput against an iperf3 server, either a public server over your WAN or a Linux/Windows host on your LAN. Set the client interface and port, then run with diagnose traffictest run -c .

Can a FortiGate run an iperf3 test between two of its own ports?

Yes, using diagnose traffictest server-intf and client-intf, but it only validates the interface and data path at a hardware level. It is a loopback-style connectivity check and does not push real traffic, so it is not a true throughput measurement between ports.

How do I measure download speed instead of upload on a FortiGate?

Add the -R flag for reverse mode: diagnose traffictest run -c -R. By default the FortiGate sends and the server receives (upload); reverse mode makes the server send and the FortiGate receive (download). Always test both directions.

Does FortiOS 7.2 still support diagnose traffictest?

Yes, but FortiOS 7.2.x reaches end of support in September 2026, so plan an upgrade to 7.4 or 7.6 (7.6.6 is widely recommended). FortiOS 8.0 exists but is not yet recommended for production firewalls.