What is ethtool?

What is ethtool?

Ethtool is a command-line utility in Linux® used for managing and configuring network interfaces. It allows users to query or modify network device settings such as speed, duplex mode, and auto-negotiation. Ethtool is especially valuable for monitoring and troubleshooting network performance by providing detailed information about the device's capabilities and status. While primarily used by system administrators, it is accessible to any Linux® user aiming to control or optimize their network interface behavior.

What are the primary functions of ethtool?

Ethtool provides various functions to manage network interfaces, including viewing device-specific information, adjusting speed and duplex settings, enabling or disabling auto-negotiation, and monitoring link status. It also supports the configuration of offload settings like checksum offloading. These capabilities are crucial for diagnosing issues, optimizing network performance, and customizing device behavior. Ethtool's functions make it a versatile tool for Linux®-based network management and hardware inspection.

How do ethtool and ip link differ?

Ethtool and ip link are both Linux® networking tools but serve different purposes. ethtool is used for managing and querying ethernet device settings, such as speed, duplex, and offload features. It focuses on hardware-specific configurations. On the other hand, ip link is part of the iproute2 suite and is used for managing network interfaces, like bringing them up/down, setting MTU, or changing MAC (Media Access Control) addresses. It provides broader interface management, while ethtool is more hardware centric.

What are the common commands used with ethtool?

Some common ethtool commands include ethtool to display information about a network device, ethtool -s to change settings like speed or duplex, and ethtool -i for driver and firmware details. Other commands like ethtool -S show statistics, while ethtool -k displays offload features. Each command offers targeted functionality, addressing different aspects of network management and troubleshooting.

What is the command to use ethtool on all interfaces?

To query all network interfaces using ethtool, you can use a loop in the terminal:

for iface in $(ls /sys/class/net); do ethtool $iface; done

This command lists all interfaces in /sys/class/net and runs ethtool on each. It's helpful for checking ethernet settings like speed, duplex, and link status across all interfaces. Remember, ethtool requires root privileges, so use sudo if necessary. This ensures you gather detailed information for every interface on the system.

What is the output of the ethtool command?

The output of ethtool shows kernel-level port settings, such as:

Settings for eth0:

Speed: 1000Mb/s

Duplex: Full

Auto-negotiation: on

Link detected: yes

It reflects the interface's speed, duplex mode, auto-negotiation, and link status. The switchd process ensures hardware and kernel settings (like speed and link detection) remain synchronized. This output is crucial for diagnosing and managing ethernet configurations effectively.

Does ethtool support changing network interface settings?

Yes, ethtool allows users to modify network interface settings. For example, users can alter the speed, duplex mode, and auto-negotiation of a connected device. Additionally, it supports enabling or disabling offload features and wake-on-LAN functionality. These changes can optimize network performance to suit specific requirements or resolve issues. By providing granular control over these settings, ethtool becomes a powerful tool for network management.

Does ethtool allow enabling or disabling specific features of a network interface?

Yes, ethtool enables and disables various network interface features. For example, users can control offload features like TCP checksum or scatter-gather through ethtool -K . Wake-on-LAN functionality can also be toggled using ethtool -s wol. These options provide fine-grained control for specific networking scenarios, helping customize the interface’s functionality to match operational needs or performance requirements.

Can ethtool display the supported link modes of a network interface?

Yes, ethtool can display the supported link modes of a network interface. By running ethtool , users can view details like supported and advertised speeds, duplex modes, and auto-negotiation capabilities. This information helps in understanding the capabilities of a network device and can guide decisions during setup or troubleshooting, such as ensuring compatibility between network components.

What is the process to install ethtool on a Linux® system?

Installing ethtool on a Linux® system is straightforward and depends on the distribution. For Debian-based systems, use sudo apt install ethtool, while Red Hat-based systems can use sudo yum install ethtool or sudo dnf install ethtool. Once installed, it provides immediate access to its suite of commands. Many modern Linux® distributions include ethtool pre-installed, but verification with which ethtool can confirm its presence.

How to check ethtool version?

To check the version of ethtool installed on your system, use the following command:

ethtool --version

This will display the version number of the ethtool utility, for example:

ethtool version 5.19

Knowing the version is useful for ensuring compatibility with your system and accessing the latest features or bug fixes. If the command doesn't work, ensure ethtool is installed, or use your package manager to update it.

Does ethtool provide information about driver and firmware versions?

Yes, ethtool offers driver and firmware version details for network devices. By using the command ethtool -i , users can retrieve information about the network driver, its version, and firmware details. This is particularly useful for diagnosing compatibility issues or ensuring that devices are running the latest supported software versions.

Can ethtool display link-level details about network cables?

Yes, ethtool can provide link-level details such as signal strength and cable diagnostics if supported by the driver and hardware. Using ethtool --cable-test , users can test network cables for issues like faults or poor connection quality. This feature is particularly helpful for troubleshooting physical network problems in complex setups.

Can ethtool check for full-duplex or half-duplex network status?

Yes, by running ethtool , users can see whether their network connection is operating in full-duplex or half-duplex mode. Full-duplex allows simultaneous sending and receiving of data, improving performance, while half-duplex limits one direction at a time. Understanding this status helps in diagnosing performance issues and optimizing network connections.

Can ethtool be used with bonded network interfaces?

Yes, ethtool works with bonded network interfaces, but commands target individual physical interfaces in the bond. For example, administrators can use it to check hardware capabilities or configure settings on each physical interface. This ensures that bonded interfaces operate optimally, improving reliability and performance for aggregated network links.