Background: I have a 40 Mbps Ethernet connection hooked directly to my iMac running on Mojave.

I use the Mac as a router to share the internet connection from Ethernet to other devices using WiFi.

Problem: WiFi-connected devices are easily hitting 15-20 Mbps download speeds, but the Mac, being directly connected to Ethernet, only reaches download speeds up to 4 Mbps!

I don't know what's the reason behind this.

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    There's a python based speedtest brew install speedtest-cli you might want to try if you aren't measuring the speeds from the router. I'm able to see full bandwidth on ubiquiti / speed test and all Macs in the last 10 years should be able to get 40Mbit over ethernet if there's not a problem with the OS or software. How are you measuring the bandwidth? (and does it show buffer bloat or can you control for other devices hogging the bandwidth) – bmike Apr 20 '19 at 22:37
  • See on speed test results it's showing 40 now it's not a 1:1 connection so after dividing I am supposed to get around 15 down; which is true, but, the issue is with the mac for example if I download a 1GB file on my mac, the internet speed remains within 4 Mbps max whereas the same file downloads on my phone at a speed of 10-15 Mbps – Sayan Apr 20 '19 at 22:45
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    @Sayan - can you describe how the iMac is being used as a router for all the other devices a bit more? The networking setup is confusing in your description. – slm Apr 21 '19 at 3:58
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    @slm My Mac directly connects to the internetet via the Ethernet port, now I use the internet sharing menu under system preferences to broadcast the Mac's internet over WI-FI to other devices – Sayan Apr 21 '19 at 6:20
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    Does the problem disappear when you turn off the WiFi routing? – IconDaemon Apr 21 '19 at 12:31

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