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"I'm experiencing slow network speeds with my Fortinet Ethernet adapter. Any suggestions?

Hi everyone,


I'm experiencing slow network speeds with my Fortinet Ethernet adapter. I'm getting download speeds that are fine, but my upload speeds are always between 10-12Mbps, even though I recently upgraded my bandwidth to 50/50. Does anyone have any suggestions on how I can troubleshoot and improve the performance of my Ethernet adapter?
Here are some things I've tried so far:


Checked for any firmware updates for my Fortinet Ethernet adapter


Restarted my router and modem


Checked for any background applications that might be using up bandwidth


However, none of these steps have improved my upload speeds. Any suggestions would be greatly appreciated.


Thank you!


Hello Charlesdevis,

Please answer the below questions
1.) May I know if the issue is for all users or some users?
2.) May I know the forticlient version and fortiOs version?
3.) May I know if you enabled any traffic shaping in the Policy of SSLVPN users?



How are you testing the speed (using websites like speedtest or iperf)? Can you bypass fortigate and check the upload speed to confirm if the issue is with firewall or not. If the you are getting the expected speeds after bypassing the firewall, I would suggest to create a test firewall policy without any UTM features/inspection and then test the traffic.

you may also explore the builtin iperf tool.



- Have you found a solution? Then give your helper a "Kudos" and mark the solution.

Contributor III

When experiencing slow upload speeds with your Fortinet Ethernet adapter, here are a few additional suggestions you can try to troubleshoot and improve performance:

1. Check for network congestion: Determine if there is any network congestion or heavy traffic on your network. You can try uploading files during off-peak hours to see if the performance improves. Additionally, check if other devices on the network are also experiencing slow upload speeds, as this could indicate a network-wide issue.

2. Verify cable and connection: Ensure that the Ethernet cable connecting your Fortinet Ethernet adapter to your router or modem is in good condition and properly seated. Faulty or damaged cables can cause performance issues. Try using a different Ethernet cable to rule out any cable-related problems.

3. Adjust duplex settings: In some cases, mismatched duplex settings between the Fortinet Ethernet adapter and the connected device (router, modem, or switch) can result in slow performance. Access the settings for the Fortinet Ethernet adapter and ensure that the duplex settings are correctly configured to match the connected device. Common options are Auto Negotiation, Full Duplex, or Half Duplex.

4. Check for driver updates: Visit the Fortinet support website or contact their support team to check for any driver updates specifically for your Fortinet Ethernet adapter. Updated drivers can sometimes improve performance and address compatibility issues.

5. Adjust Quality of Service (QoS) settings: QoS settings on your router or FortiGate firewall can prioritize or limit bandwidth for certain types of traffic. Check the QoS settings to ensure that your upload traffic is not being throttled or deprioritized. You may need to consult the Fortinet documentation or seek assistance from their support team for specific instructions on adjusting QoS settings.

6. Perform a speed test: Use online speed testing tools to measure your upload speeds accurately. This will help you determine if the slow upload speeds are specific to your Fortinet Ethernet adapter or if they are more broadly related to your internet service provider (ISP) or network infrastructure.

If none of these steps resolve the slow upload speed issue, it is recommended to contact Fortinet support or your ISP for further assistance. They can provide you with specific guidance and help diagnose any potential issues with your network or the Fortinet Ethernet adapter.

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