Ethernet and tethering

Ethernet on a Mac is slower than expected

An Ethernet link runs at the speed that both ends and the cable support. A slow link often comes from the cable, an adapter or a hub.

Applies to: macOS 13 Ventura and later for System Settings > Network > Details > Hardware. The commands work in all current macOS versions.Checked: 29 October 2026

Symptoms

Ethernet is not faster than Wi-Fi, or it is slower.
Speed tests stop near 100 Mbit/s on a faster connection.
The speed changes when you use another cable or port.

Likely causes

The cable. Apple says that Gigabit Ethernet needs a Gigabit Ethernet cable. An old or damaged cable can give 100 Mbit/s only.
The adapter or port. A USB 2.0 port or hub has a maximum of 480 Mbit/s. It cannot carry Gigabit Ethernet at full speed.
A manual setting. A speed or duplex that someone set by hand can stop the link from using its full speed.
The other end. The router or switch port can support a lower speed.

How to check

Find the device name of the Ethernet port.
```
networksetup -listallhardwareports
```
Show the media setting and the active media. Replace en5 with your device.
```
networksetup -getMedia en5
```
Output A Current line and an Active line, for example autoselect and the negotiated media.
See the negotiated link in the media line. 1000baseT is 1 Gbit/s and 100baseTX is 100 Mbit/s.
```
ifconfig en5 | grep media
```
Choose Apple menu > System Settings > Network. Click the Ethernet service, then click Details. Click Hardware.
Make sure that Configure is set to Automatic.

How to fix it

Use a cable that supports Gigabit Ethernet, such as Cat 5e or better.
Connect the adapter directly to the Mac, not through a USB 2.0 hub.
Try another port on the router or switch.
If Configure is Manual and nobody told you to set it, set it to Automatic. Click OK.
Set the speed by hand only if your network administrator gives you a value. Apple says that wrong settings can reduce performance.
To go back to automatic media and MTU from Terminal, use this command.
```
sudo networksetup -setMTUAndMediaAutomatically en5
```
Needs an administrator password.

With Kilobat

Test the speed to another computer on your local network. Install iperf3 on this Mac, and run iperf3 -s on the other computer.
```
kilobat lan-test 192.168.1.20
```
Test the internet speed and the latency under load. It uses up to 80 MB.
```
kilobat speedtest
```

Questions

Does a faster link make the internet faster?

Only if the link is the slowest part. If your internet plan is slower than the link, the plan sets the speed.

Should I set duplex by hand?

No, not unless your network administrator tells you. Apple recommends the automatic settings.

Sources

Apple Support: Use Gigabit Ethernet on Mac
Apple Support: Change Hardware settings on Mac
networksetup(8), man page installed with macOS 27.2
ifconfig(8), man page installed with macOS 27.2

Sources checked on 29 October 2026. Man pages are the ones installed with macOS; open one with man <name> in Terminal.