Slow download rate on a Raspberry PI 4

Hi,
I’m facing slow download rates and just have seen a few other threads here but without a solution.

Operating on Raspberry PI 4 with 2 GB RAM. Green is connected with built-in LAN to internal network and red0 is connected to the modems switch. via USB ethernet adapter.

Directly connecting the laptop to the modem results in speedtest with 266.80 Mbps download rate. Executing speedtest on ipfire results in 107 Mbps.

Somehow the green and red adapter seem to be restricted to about 100-130 Mbits/sec.

Output of iperf3 on green0:

[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec  15.1 MBytes   127 Mbits/sec    0    600 KBytes       
[  5]   1.00-2.00   sec  15.0 MBytes   126 Mbits/sec    0    864 KBytes       
[  5]   2.00-3.00   sec  16.2 MBytes   136 Mbits/sec    0    919 KBytes       
[  5]   3.00-4.00   sec  13.8 MBytes   115 Mbits/sec    0    919 KBytes       
[  5]   4.00-5.00   sec  16.2 MBytes   136 Mbits/sec    0   1.05 MBytes       
[  5]   5.00-6.00   sec  13.8 MBytes   115 Mbits/sec    0   1.05 MBytes       
[  5]   6.00-7.00   sec  13.8 MBytes   115 Mbits/sec    0   1.05 MBytes       
[  5]   7.00-8.00   sec  15.0 MBytes   126 Mbits/sec    0   1.05 MBytes       
[  5]   8.00-9.00   sec  15.0 MBytes   126 Mbits/sec    0   1.05 MBytes       
[  5]   9.00-10.00  sec  11.2 MBytes  94.3 Mbits/sec    0   1.05 MBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec   145 MBytes   122 Mbits/sec    0             sender
[  5]   0.00-10.02  sec   142 MBytes   119 Mbits/sec                  receiver

Output of ethtool green0:

Speed: 1000Mb/s
	Duplex: Full
	Auto-negotiation: on

Output of red0:

Speed: 1000Mb/s
	Duplex: Full
	Auto-negotiation: on

I don´t have enabled any proxy settings or other filter on ipfire nor QoS.

Any ideas?

If you are seeing 100-130 Mbits/sec you are doing very well. The raspberry pi 4B is just not powerful enough to do better.

The RPi4B is better suited for slower speed connections and it what I recommend for people with 50 mbps download and 10 mbps upload.

1 Like

RPi tried really well to produce the Pi4, But there are a few issues they could not work out on it due to the layout.

The Ethernet controller and USB controller are too close to each other and the ports and as a result the heat dissipation is hindered. Putting small tape on heat sinks on them solves this issue, but because the bus legnth is too short on the USB, standing waves occur when the usb goes into super speed and causes the port communication to slow down due to this interference. Using a USB hub with a minimum of 3Ft (~1M) cord will dampen this standing wave. If you ever hear about people having issues with usb NVMe drives that is why (standing waves) .