Linux Ethernet Not Working: Check the Network Stack in Order
An Ethernet cable can have link while IP configuration or DNS still fails. Diagnose the path from hardware to application instead of changing everything at once.
Short answer
When Linux Ethernet fails, check the layers in order: device detection, physical link, driver, connection manager, address assignment, route, DNS and finally the application. A “connected” icon only proves part of that path.
Ethernet troubleshooting order
| Layer | Evidence to collect | If it fails |
|---|---|---|
| Hardware/device | lspci or lsusb for the exact adapter. | Confirm device identity, dock/adapter connection and kernel detection. |
| Link | ip link and switch/router link indicators. | Check cable, port, adapter and negotiated link state. |
| Connection | nmcli device status on NetworkManager systems. | Inspect the active profile and connection errors. |
| Address | ip addr | Investigate DHCP/static configuration. |
| Route | ip route | Confirm a usable default route/gateway. |
| DNS | Resolver status/query tests. | Repair DNS only after IP routing works. |
USB adapters add one more hardware-revision variable
A USB Ethernet model can change internal hardware across revisions, and vendor driver support can differ by revision. The TP-Link UE300C is useful as a fallback because TP-Link currently lists Linux/Ubuntu support and publishes Linux driver information for recent hardware versions, but that does not make every USB Ethernet product universally Linux-compatible.
Avoid replacing network configuration with a generic static IP
Assigning a guessed static address can create duplicate addresses, wrong gateways or DNS errors. If DHCP is failing, determine why the lease is not obtained. A temporary static configuration is a diagnostic tool only when you know the network’s correct addressing.
Remote-system warning
If you are changing Ethernet configuration over SSH, a wrong profile or route can immediately remove your access. Schedule an on-site or console recovery path before modifying a remote production machine.
Useful gear for this task
Official references
For current behavior and version-specific details, use the relevant upstream documentation alongside this guide.
Frequently asked questions
Why does Ethernet show connected but the internet does not work?
A physical link can be up while DHCP, routing, DNS, VLAN configuration or upstream networking is still wrong. Check each layer separately rather than replacing the driver immediately.
How can a USB Ethernet adapter help?
A supported USB Ethernet adapter can provide an independent network path for troubleshooting or temporary connectivity. It does not repair the built-in Ethernet controller or Wi-Fi device.