There are multiple reasons why you might want to test the speed of you local network. For example you can test the speed between your router and your device. Or the speed between your device and a home server. For me it was the former. I wanted to make sure the connection from my router to my desktop PC was working fine so that I could make the most of the broadband speed I was paying for.
We can use a tool called IPerf3. This is available for many platforms including: Windows, Linux, Mac and Android. I installed it on my PC, but I cannot run it on my router, so I installed it on my laptop and connected it directly to another ethernet port on the router.
On one device run the server:
iperf3 -s
On the other device run the client pointing to the IP of the first device to start the test:
iperf3 -c 192.168.0.123
You'll get some results that look like this:
❯ .\iperf3.exe -c localhost
Connecting to host localhost, port 5201
[ 4] local ::1 port 53076 connected to ::1 port 5201
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-1.00 sec 2.08 GBytes 17.8 Gbits/sec
[ 4] 1.00-2.00 sec 2.02 GBytes 17.2 Gbits/sec
[ 4] 2.00-3.00 sec 2.06 GBytes 17.8 Gbits/sec
[ 4] 3.00-4.00 sec 2.53 GBytes 21.7 Gbits/sec
[ 4] 4.00-5.00 sec 2.48 GBytes 21.3 Gbits/sec
[ 4] 5.00-6.00 sec 2.43 GBytes 20.8 Gbits/sec
[ 4] 6.00-7.00 sec 2.52 GBytes 21.6 Gbits/sec
[ 4] 7.00-8.00 sec 2.11 GBytes 18.1 Gbits/sec
[ 4] 8.00-9.00 sec 2.10 GBytes 18.1 Gbits/sec
[ 4] 9.00-10.00 sec 2.57 GBytes 22.1 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-10.00 sec 22.9 GBytes 19.7 Gbits/sec sender
[ 4] 0.00-10.00 sec 22.9 GBytes 19.7 Gbits/sec receiver
iperf Done.
Here the average speed was 19.7 Gbits/sec.
(Note that this was unrealistically high, because in this case, I ran it against localhost, i.e. the same device.)