1. Introduction

It’s a good practice to verify that any newly installed hardware operates correctly. While there are many hardware modules in a computer, we’ll focus on the NIC (Network Interface Card).

In this tutorial, we’ll learn how to verify that the NIC has the correct network speed using two different ways: with standard Linux tools, and with the ethtool command.

2. Using Standard Linux Tools

We can check the speed of our NIC module by using the /sys pseudo-filesystem:

$ cat /sys/class/net/<interface>/speed

The advantage of this method is that we don’t need to install any external software tools.

Before we run the command, we need to know the network interface name. Two easy ways to find it are by using the ifconfig command or the ip command. Of course, we can always just list the interfaces within the /sys/class/net/ directory:

$ ls /sys/class/net
bond0  bonding_masters  dummy0  eth0  lo  sit0  tunl0

Once we know the network interface name, we can run the cat command on its speed file. For example, if the interface name is eth0, here’s the command to execute:

$ cat /sys/class/net/eth0/speed

The output is 100, which means that the speed of our networking interface is 100 Mbit/s.

3. Using the ethtool Command

Another way of checking the speed of our NIC is to use the ethtool command. ethtool is a useful utility to get the settings of the networking devices on a system.

As our main focus is the network speed, we’ll filter the ethtool output for the speed by using the grep command, for example:

$ sudo ethtool eth0 | grep Speed
Speed: 100Mb/s

The command above consists of multiple sub-commands. Let’s look at them in more detail:

  • sudo provides root access
  • ethtool is the main command
  • eth0 is the interface name
  • grep Speed filters the ethtool output through a | pipe for the actual speed

As a result, we’ve obtained the speed of our NIC in a readable form. Further, it matches the information we already have from /sys/class/net/.

4. Conclusion

In this article, we learned how to find the speed of our NIC. Firstly, we looked at the standard Linux tool, where we checked the /sys/class/net/<interface>/speed file. And secondly, we learned how to use the ethtool command to filter out the same speed information.

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