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How To Set MTU Permanently in Ubuntu 20.04 CLI for WSL2

Ubuntu 6

Setting the Maximum Transmission Unit (MTU) in Ubuntu 20.04 CLI for WSL2 is an essential task for network administrators. The MTU defines the maximum size of a packet that can be sent over a network connection. Setting the MTU to an optimal value can improve network performance and efficiency.

This guide will walk you through the process of setting the MTU permanently in Ubuntu 20.04 CLI for WSL2.

Quick Answer

To set the MTU permanently in Ubuntu 20.04 CLI for WSL2, you can either use the NetworkManager GUI, edit the NetworkManager connection file, or modify the dhclient configuration file. These methods allow you to specify your desired MTU value, which will be used for all future network connections.

Understanding MTU

MTU stands for Maximum Transmission Unit. It is the size (in bytes) of the largest protocol data unit that the layer can pass onwards. MTU parameters usually appear in association with a communications interface (NIC, serial port, etc.). Standards (Ethernet, for example) can fix the size of an MTU; or systems (such as point-to-point serial links) may decide MTU at connect time.

Prerequisites

Before we begin, ensure that you have the following:

  • Ubuntu 20.04 installed in WSL2
  • Sudo or root access to the Ubuntu system

Setting MTU Permanently in Ubuntu 20.04 CLI for WSL2

Using NetworkManager GUI

  1. Open the NetworkManager GUI by running the command nm-connection-editor in the terminal. This command opens up the NetworkManager GUI, where you can modify the network connections.
  2. Select the network connection you want to modify and click on the “Edit” button.
  3. In the “IPv4” or “IPv6” tab, depending on your network configuration, find the “MTU” field and enter your desired MTU value. This value is the maximum size of a packet that can be sent over the network connection.
  4. Click “Save” to apply the changes. The new MTU value will be used for all future network connections.

Editing the NetworkManager Connection File

  1. Open the NetworkManager connection file for the specific network interface using the command sudo nano /etc/NetworkManager/system-connections/yourconnectionname.nmconnection. This command opens the connection file in the nano text editor.
  2. Locate the line that starts with mtu= and change the value to your desired MTU value.
  3. Save the file and exit the editor. The new MTU value will be used for all future network connections.
  4. Restart the NetworkManager service using the command sudo systemctl restart NetworkManager. This command restarts the NetworkManager service, applying the new MTU value.

Modifying the dhclient Configuration File

  1. Open the dhclient configuration file using the command sudo nano /etc/dhcp/dhclient.conf. This command opens the dhclient configuration file in the nano text editor.
  2. Add the following lines to set the default and supersede MTU values:
default interface-mtu <your_MTU_value>;
supersede interface-mtu <your_MTU_value>;

These lines set the default and supersede MTU values. The default value is used if no other value is specified. The supersede value overrides any other values.

  1. Save the file and exit the editor. The new MTU values will be used for all future network connections.
  2. Restart the networking service using the command sudo systemctl restart networking. This command restarts the networking service, applying the new MTU values.

Conclusion

Setting the MTU value can greatly improve network performance and efficiency. This guide has shown you how to set the MTU permanently in Ubuntu 20.04 CLI for WSL2. Remember to choose the method that best fits your specific network configuration and tools.

What is the default MTU value in Ubuntu 20.04 CLI for WSL2?

The default MTU value in Ubuntu 20.04 CLI for WSL2 is typically 1500.

How can I check the current MTU value in Ubuntu 20.04 CLI for WSL2?

You can check the current MTU value by running the command ip addr show in the terminal. Look for the MTU value listed next to your network interface.

Can I set different MTU values for different network interfaces in Ubuntu 20.04 CLI for WSL2?

Yes, you can set different MTU values for different network interfaces. Follow the steps mentioned in the guide for each network interface you want to modify.

Will changing the MTU value affect my internet speed?

Changing the MTU value can potentially improve network performance and efficiency, but the impact on internet speed may vary depending on your specific network configuration and internet service provider. It is recommended to experiment with different MTU values to find the optimal setting for your network.

Do I need to restart my system after changing the MTU value?

No, you do not need to restart your system. However, you may need to restart the NetworkManager or networking service for the changes to take effect. The guide provides instructions on how to restart these services.

Can I revert back to the default MTU value?

Yes, you can revert back to the default MTU value by either removing the MTU configuration from the NetworkManager connection file or the dhclient configuration file, depending on the method you used to set the MTU. Restart the respective services after making the changes.

Will setting a larger MTU value always improve network performance?

Setting a larger MTU value may improve network performance in certain scenarios, such as when transferring large files over a high-speed network. However, it is not a guaranteed improvement and can sometimes lead to fragmentation issues or compatibility problems with certain network devices. It is recommended to test and monitor the network performance after making any MTU changes.

Can I set the MTU value for a wireless network connection?

Yes, you can set the MTU value for a wireless network connection in Ubuntu 20.04 CLI for WSL2. Follow the steps mentioned in the guide, but instead of editing the NetworkManager connection file, select the appropriate wireless network connection in the NetworkManager GUI and modify the MTU value in the "IPv4" or "IPv6" tab.

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