USB-C dock or Ethernet adapter keeps disconnecting on Mac

A dock or a USB Ethernet adapter adds a hub, a chip and a power path between the Mac and the cable. Find when the link goes down, then remove one part at a time.

Fix this with your agentCopies a prompt for Claude Code, Codex or any agent that can use Terminal.

My Mac has this problem: USB-C dock or Ethernet adapter keeps disconnecting on Mac. Read https://kilobat.app/guides/ethernet-keeps-disconnecting-mac.md and work through it with me. Install the Kilobat CLI if it’s missing: brew install seifip/kilobat/kilobat. Run the guide’s Terminal and kilobat checks yourself and tell me what you find. List the steps only I can do. Ask before you change any setting.

Applies to: macOS 14 Sonoma and later for the System Settings steps. The Terminal commands work on all current versions.Checked: 7 November 2026

Symptoms

The Ethernet service in Network settings changes between Connected and Not Connected.
Calls, downloads or SSH sessions stop for a few seconds, then continue.
The dock or adapter works after you connect it again, then fails later.
The connection fails after the Mac wakes from sleep.
Other devices on the dock, such as a display or a drive, disconnect at the same time.

Likely causes

Too little power for the dock or adapter. Apple says that a self-powered hub must be connected to its AC adapter. A bus-powered chain of devices can also get too little power.
A hub between the adapter and the Mac. Apple says that the device and the hub must have the same USB speed. Many docks contain a hub.
The adapter's chip and its software. macOS supports some Ethernet chips without extra software. Apple does not publish a list. The adapter's maker says if it needs a driver or a firmware update.
Sleep and wake. After sleep, the dock and the adapter must start again. A drop that occurs at each wake points to this.
The cable or the switch port. A damaged cable or a bad port makes the link go down and up. The link speed can also change each time.

How to check

Find the device name of the adapter, for example en7.
```
networksetup -listallhardwareports
```
Look at the link state and the negotiated speed. Replace en7 with your device.
```
ifconfig en7 | grep -E 'status|media'
```
Output A status: active line, and a media: line such as 1000baseT <full-duplex>.
Watch the routing changes while you work. A drop shows as a burst of messages for the interface.
```
route -n monitor
```
Look at the error counters of the interface. Errors that increase point to the cable or the port.
```
netstat -I en7
```

Compare the drop times with the sleep and wake times.

pmset -g log | grep -E ' (Sleep|Wake|DarkWake) ' | tail -20

Hold the Option key and choose Apple menu > System Information. Make sure that the adapter is under USB or Thunderbolt.
Check if other devices on the dock disconnect at the same time. If they do, the cause is the dock, not the network.

How to fix it

If the dock has its own power adapter, connect it. Use the power adapter that came with the dock.
Connect the Ethernet adapter directly to a port on the Mac, not through a hub.
Disconnect the other devices from the dock. Connect them again one at a time to find the one that causes the problem.
Install all macOS updates. Choose Apple menu > System Settings > General > Software Update.
Read the dock or adapter maker's support page. Install the driver or firmware update that it gives for your macOS version.
Replace the Ethernet cable with a cable that you know works. Try a different port on the router or switch.
If the speed changes at each drop, see Ethernet on a Mac is slower than expected.
If the adapter disappears from Network settings, see Mac does not detect a USB or Thunderbolt Ethernet adapter.
Shut down the Mac. Turn off the router or switch, wait a few minutes, then turn it on. Then start the Mac.

With Kilobat

The Kilobat app records each drop while it runs. Show the drops with their start and end times.
```
kilobat outages
```
Output Events such as Unreachable and Network changed.
Show the router, internet and DNS checks over the last day.
```
kilobat health-history --hours 24
```
See the counters of each physical interface. A counter that stops shows when the adapter stopped.
```
kilobat interfaces --json
```
Find which layer fails while the link is down.
```
kilobat diagnose
```
A gap in the history means that the app did not run. It does not prove that the connection worked.

Questions

Does the adapter need a driver?

It depends on the chip in the adapter. Apple does not publish a list of supported chips. Read the adapter maker's instructions for your macOS version.

Users say that Energy Efficient Ethernet on the switch causes drops. Is that true?

Some users report this, but Apple does not document it. If your switch has the setting, read the switch maker's documentation before you change it.

Is Wi-Fi a good fallback while I test?

Yes. Put Wi-Fi below Ethernet in the service order. The Mac then uses Wi-Fi when Ethernet is down. See Mac uses the wrong network connection.

Sources

Apple Support: Troubleshoot an Ethernet device on Mac
Apple Support: If a USB device doesn't work with Mac
Apple Support: If you see USB Devices Disabled on your Mac
ifconfig(8), route(8), netstat(1), networksetup(8) and pmset(1), man pages installed with macOS 27.2

Checked on 7 November 2026.