ethtool Command
Advanced Networking man(1)Display or change ethernet device settings
👁 11 views
📅 Updated: Mar 15, 2026
SYNTAX
ethtool [OPTION]... DEVNAME
What Does ethtool Do?
ethtool displays and modifies Ethernet device settings. It shows link speed, duplex mode, auto-negotiation status, driver information, and hardware features for network interfaces.
ethtool is essential for diagnosing network performance issues, verifying link speed, checking cable connectivity (link detection), and tuning network interface parameters.
ethtool works with physical and virtual Ethernet interfaces. It requires root for modifying settings but can display information without root on most systems.
ethtool is essential for diagnosing network performance issues, verifying link speed, checking cable connectivity (link detection), and tuning network interface parameters.
ethtool works with physical and virtual Ethernet interfaces. It requires root for modifying settings but can display information without root on most systems.
Options & Flags
| Option | Description | Example |
|---|---|---|
| interface | Show interface settings | ethtool eth0 |
| -i | Show driver information | ethtool -i eth0 |
| -S | Show NIC statistics | ethtool -S eth0 |
| -s | Change settings | sudo ethtool -s eth0 speed 1000 duplex full |
| -k | Show offload features | ethtool -k eth0 |
| -p | Blink LED (identify physical port) | sudo ethtool -p eth0 10 |
Practical Examples
#1 Show interface info
Shows link speed, duplex, auto-negotiation, and link status.
$ ethtool eth0
Output:
Speed: 1000Mb/s
Duplex: Full
Link detected: yes
#2 Driver info
Shows the kernel driver, version, and firmware for the NIC.
$ ethtool -i eth0
Output:
driver: e1000e\nversion: 3.8.7-k
#3 NIC statistics
Shows detailed NIC statistics including errors and drops.
$ ethtool -S eth0 | head -20#4 Blink port LED
Blinks the port LED for 10 seconds to identify the physical NIC.
$ sudo ethtool -p eth0 10#5 Check link
Quick check if a cable is connected and link is active.
$ ethtool eth0 | grep "Link detected"
Output:
Link detected: yes
Tips & Best Practices
Check link speed: ethtool eth0 | grep Speed quickly shows if you are running at 100M, 1G, or 10G. Mismatched speed = performance issue.
Blink to identify: ethtool -p eth0 10 blinks the NIC LED for 10 seconds. Essential when identifying which physical port corresponds to which interface.
Requires kernel support: Not all virtual NICs support ethtool. Cloud instances may show limited information.
Frequently Asked Questions
How do I check network link speed?
ethtool eth0 shows Speed, Duplex, and Link detected status.
How do I identify a physical network port?
sudo ethtool -p eth0 15 blinks the LED for 15 seconds so you can find the physical port.
How do I check if a cable is connected?
ethtool eth0 | grep "Link detected" shows yes if the cable is connected and the link is up.
Related Commands
More Networking Commands
Master Linux with Professional eBooks
Curated IT eBooks covering Linux, DevOps, Cloud, and more
Browse Books →