How to test bandwidth from PC to router/modem

[haughtonomous]

HI, I've recently moved home from a place with excellent broadband to erm... somewhat less excellent. My PC is unchanged (Mint 18.3, latest patches). As in my old home I'm using two powerline adapters, one at the PC (the only one) and one at the router, only about 10m apart and AFAIK on the same ring main. These worked well at my old home which was two floors, but although they are closer together and on the same floor now I suspect they (or the house electrics) are the problem here.
My question is - how can I test the netwprk performance of the link between PC and router? I've tried iperf3 using one instance as server and another as client, both on my sole PC, which reports a staggering 20Gbps bandwidth (I suspect that it is just doing some sort of loopback and cutting out the router link, which traceroute suggests) but the question remains - how can I test the bandwidth over the link between PC and router?

TIA

[senjoz]

I think that for iperf3 you need two computers. I tried your test with two instances of iperf3, server and client, on the same computer. Result was also unreal, 42 Gbits/sec.

If your problem is low speed of internet connection, connect your computer directly to the router, test internet speed with one of speed test webpages and compare that result to the same test made with a computer connected through your powerline adapter(s).

Regards, Jože

[haughtonomous]

Thanks, you have confirmed my own conclusions. However the router shows that the the download speed from the internet far exceeds the bandwidth that an internet speed test on my PC shows so the problem is not with the internet, it appears to be from PC to router and may well be the powerline devices (which should be Gigabit performance). That's why I need to test the bandwidth of that segment alone to prove it. Hence my question.

[haughtonomous]

I've actually connected the PC to the router with an ethernet cable lying along the floor (wife was not happy!) and it shows a dramatic improvement, so I guess that proves that the powerline arrangement is not working well. I'll probably have to install a permanent ethernet cable link which isn't going to go down well domestically! Ah well.

I'd still like to know how to test the PC->powerline->router link itself, to get some actual data....

[djph]

I'd still like to know how to test the PC->powerline->router link itself, to get some actual data....

You can't. iperf on 2 PCs would be the closest approach.

[senjoz]

Ask one familiar or friend for assistance with his computer, connect it to the router lan port and start there iperf3 server, iperf3 -s. It can be also a Windows machine. iperf3 can run on Windows. Measure network speed to your computer on the other end of the powerline with iperf3 client, for instance iperf3 -c server_ip_address -i 1 -t 13 -w 4M -p 4 -O 3.

Another possibility would be to run iperf3 server on the router. Some routers with dd-wrt firmware and Asuswrt-Merlin with Entware can do that.

Regards, Jože

[haughtonomous]

Thank you all for the help. I don't have a "friend with a computer", having recently moved to a different part of the country so I'll have to accept for now that the powerline system is most likely the problem, and put up with it or install a fixed ethernet cable to the router. (I've tried a USB wireless adapter before but I never got it to work.)