I'm using a Fortigate 70F and experiencing lower bandwidth in download then upload for all speed tests done from a computer and internet mode. The CPU of the Fortigate doesn't going to 100% during the speed test. The version of FortiOS is 7.0.12. I'm connected to a WAN port of the firewall. No limit bandwidth policie are applied. My LAN connection is wired gigabyte. Thank you for commenting on the reason for this situation or provide a solution to get the full internet bandwidth or at least the same as upload speed.
Especially when you're using a laptop for speed testing, make sure that laptop has a physical GigE port built in. If an USB adapter or something additional, most unlikely you can see closer to physical port speed 1Gigbps. Then also you should put it in Safe mode with Networking (for Windows). Otherwise, many applications are listening to inbound traffic for their own ports at the same NIC, which might bog down download speed.
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