Thank you for reaching out. Based on your setup, the high packet loss you’re experiencing is most likely caused by a missing bandwidth limit in your iPerf3 command. Without it, UDP traffic can flood the router’s buffer faster than it can process, resulting in dropped packets.
Please try updating your client command as follows:
iperf3 -c -u -p 5001 -b 50M -i 5
The -b flag sets the target bitrate. We recommend starting at 50M and adjusting up or down based on results. You can also remove the -w 100M flag for now, as the large window size may be contributing to buffer saturation.
Additionally, please verify the following:
The server is bound to the correct LAN IP - Run “ip addr” to confirm, and ensure the -B flag references your LAN interface address, not a WAN or mobile interface.
Run a quick TCP test to isolate the issue - Use “iperf3 -c -p 5001 -i 5” (no -u flag). If TCP works cleanly, the issue is specific to UDP handling.
In most cases, adding the -b flag resolves the issue immediately. Please give it a try and let us know how it goes.
Verify the server binds to the correct LAN IP under Network → LAN using:
iperf3 -s -p 5001 -B
5. Direct Connection Test
Connect routers directly with a cable to rule out switches or intermediate devices.
Firmware and Offloading
Ensure the latest RutOS firmware is installed (System → Firmware).
Toggle Software Flow Offloading if available (Network → Routing/NAT Offloading).
Optional: Traffic Shaping
Use Network → Traffic Shaping to control UDP rates if needed for testing.
Note: The extreme packet loss at modest UDP rates indicates internal router limitations rather than network faults. These steps focus on confirming and mitigating those limits.