CompTIA Linux+ (XK0-006)TroubleshootingMedium
A Linux server is experiencing extremely slow network performance, but CPU utilization and disk I/O appear normal. The administrator suspects an issue with the network interface's duplex settings, potentially causing a duplex mismatch. Which command would allow the administrator to check the current speed and duplex settings of the `eth0` network interface?
- A`ethtool eth0`
- B`cat /sys/class/net/eth0/speed`
- C`ifconfig eth0`
- D`ip link show eth0`
Show answer & explanationAnswer & explanation
Correct answer: A. `ethtool eth0`
`ethtool` is the dedicated command-line utility for querying and controlling network device driver and hardware settings, including speed, duplex, autonegotiation, and other advanced parameters essential for diagnosing physical layer network issues.
Why the other options are wrong
- B. `cat /sys/class/net/eth0/speed` only shows the link speed, not the duplex mode or other detailed settings.
- C. `ifconfig eth0` (deprecated in many modern distributions) provides basic IP and link information, but typically lacks detailed speed and duplex settings found in `ethtool`.
- D. `ip link show eth0` provides basic link status, MAC address, and queue information, but not duplex settings.
ethtool for Duplex Settings
`ethtool` is a utility used to query or control network interface card (NIC) settings, including critical parameters like speed and duplex mode, which are vital for network troubleshooting.
- Provides detailed hardware-level information about a NIC.
- Can show current speed (e.g., 1000Mb/s), duplex (Full/Half), and autonegotiation status.
- Useful for diagnosing duplex mismatch, which can severely degrade network performance.
Memory trick: Use the 'eth'tool to see 'eth'ernet settings like duplex and speed.