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Success! It was only a 2m ethernet cable, but I hope to use about 40m in order to set this up at the bottom of the garden to monitor the webcams in my bird boxes. I’d expect a single 2.5Gbps port to outdo a pair of slower ones, unless it really does choke the CPU.This weekend I tested powering my Raspberry Pi and two webcams via a simple passive Power Over Ethernet (PoE) adapter. Given my iperf3 result with the onboard Ethernet, I’d expect pair bonding two 1Gbps ports to hit about 1.6-1.8 Gbps.Anything in the 1.8* Gbps-2.2Gbps range would seem to indicate it’s working well. If it’s (1), I’d expect good results with the 2.5GbE adapter. Is that 2.4 Gbps because (1) each USB 3.0 port gets half the available 5 Gbps of the USB 3 bus, shared between them or (2) the CPU itself really is that much of a bottleneck? That’s 2.4 Gbps on a bus with a theoretical max speed of 5 Gbps. On a read test using hdparm, I see ~300MB/sec, which from Jeff Gearling’s results is exactly what I should be seeing on a drive going as fast as it can on that bus. Certainly fast enough not to come anywhere close to being a bottleneck on a Pi. … Okay, it’s 20Gbps, whatever that flavor of USB is this week. I’ve got a USB 3.2Gen2x2 (?!) enclosure for an MVME drive that I’m using as my boot drive. I think the CPU is definitely a bottleneck. I didn’t realize the USB3 connection could work at up to 4 Gbps.
![ethernet testing with raspberry pi ethernet testing with raspberry pi](https://www.raspberrypi.com/app/uploads/2016/08/Overview-RPi-netboot.jpg)
Watching him got me interested in pushing my Pi further, even if I don’t really have a great need to do so.
ETHERNET TESTING WITH RASPBERRY PI HOW TO
(I saved the results and may try to figure out how to make a fun graph out of them.) I’ve never even set up a VLAN before, so…one thing at at time. Average was around 867 Mbps or so, which is what I would think would be normal given overhead? I’m not using Jumbo Frames or any other optimization, as I’d need to understand not only how to do the optimization, but figure out what other devices need to also have those optimizations done and how to isolate them on a VLAN to avoid messing with the slower devices on the network. I checked with iperf3, and got 800Mbps-900Mbps off the Pi. I was definitely well off the mark, there. See: Media-independent interface - Wikipedia ) Reaching high network speeds without CPU saturation might require some tweaks. There is definitely some success in using high networking speeds with Raspberry Pi 4, though most of the efforts is done by connecting the controllers directly to the PCIe, either by using the compute module which directly exposes it (e.g.: Jeff Gerling tests with network), or by desoldering the VL806 USB3 controller and soldering a passthrough and using a “PCIe over USB cables” expansion slot. The remaining question is would the Raspberry Pi’s CPU be able to cope with the load of supporting that network speed + the USB3.0 overhead (though USB3 can require processing than USB2). So approaching 2.5 Gbps Ethernet using an USB3.0 adapter shouldn’t be impossible from a bandwidth point of view. USB3.0 has a bandwidth of ~3 Gbps (depends on the encoding mode).
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The PCIe→USB3.0 connection should be able to work at ~4 Gbps bandwidth (5 GT/s). Raspberry Pi 4 has its own dedicated RMII connection to the 1GB Ethernet.Īnd has a PCIe 2.0 single lane dedicated to the USB3.0 controller. That was true for Raspberry Pi 3 where the 1GB Ethernet was connected over the USB2.0 hub. Even the 1gb over usb3 works at 300mb only.