Linux Tactic

Mastering Default Gateways on Linux: Setting Up and Troubleshooting Made Easy

Setting Up Default Gateway on Linux Systems

Imagine sitting at your desk, eager to start working. You turn on your computer, and everything seems to be running smoothly.

However, as you try to access the internet, you receive an error message stating that the site cannot be reached. Frustrated, you wonder why this is happening, and after some research, you discover that the issue lies with your default gateway.

In this article, we’ll explore what a default gateway is, how to set it up on Linux systems, and the importance of default gateways in home networks.

Definition and Function of a Default Gateway

A default gateway can be defined as the network device that acts as an access point for data traffic to leave one network and enter another. It plays an essential role in directing internet traffic to the right destination.

When your computer sends a request to access a site or a server, it sends the request to the default gateway. The default gateway then sends the request to the next device, eventually leading to the server where the requested webpage or resource is located.

Without a default gateway, devices in one network cannot access resources or servers outside their network.

Viewing Configured Routes through IP and Route Commands

In Linux, you can view the routes that have already been configured on a system using the IP and Route commands. To view the configured routes through the IP command, use the following syntax:

ip route show

This command will display all the existing routes on your Linux system.

You’ll see a list of each network route and its destination network, subnet mask, default gateway, and interface. If you wish to view the routes through the route command, you can use the following syntax:

route -n

The above command will show you all the existing routes on your Linux system, with their destination network, subnet mask, gateway, and interface.

Deleting the Default Gateway using IP Command

In some cases, you may need to delete the default gateway from your Linux system. For example, if you’re encountering connectivity issues, or if you have received new network settings from your administrator, you may need to delete the current default gateway.

To delete the default gateway from your Linux machine using the IP command, use the following syntax:

sudo ip route delete default

Adding a New Default Gateway using Route Object with Add Argument

In Linux, you can add a new default gateway using the Route object with the Add argument. Here’s how you can add a new default gateway:

sudo route add default gw [gateway_ip]

Replace [gateway_ip] with the IP address of the default gateway you wish to assign to your Linux system.

This command assigns the default gateway to your network card and makes it the default route to the internet.

Making Routing Changes Permanent using Netplan Command

When you add or delete a default gateway, the changes you make may not be permanent. In other words, the changes you made may not persist across reboots.

To ensure that any routing changes you make remain permanent, you can use the Netplan command. Netplan is a utility for managing networking on Linux systems using the YAML format.

Here’s how you can use Netplan to make routing changes permanent:

sudo nano /etc/netplan/01-netcfg.yaml

Once you open this file in Nano, you can add the following lines of code:

network:

version: 2

renderer: networkd

ethernets:

ens33:

dhcp4: no

addresses: [192.168.1.20/24]

gateway4: 192.168.1.1

In the above code, “ens33” represents the name of your network interface card. If you’re unsure about the name of your interface card, type the “ifconfig” command in your terminal, and it will display all of your current network interface cards.

Importance of Default Gateway in Home Networks

Now that we’ve covered how to set up a default gateway on Linux systems let’s examine the importance of default gateways in home networks.

Role of Wireless Router as Default Gateway

Many households have wireless routers that provide internet access to all its devices. When configuring a home network, the wireless router is usually considered as the default gateway.

The default gateway is responsible for enabling devices in one network to access devices in another network and vice versa. Without a wireless router as a default gateway, your devices would not be able to access the internet, access other devices within your local network, or receive data from external sources.

Easy Navigation of Internet with Default Gateway

In home networks, the default gateway is the gateway to the internet. It guides network traffic to its intended destination, ensuring that your devices can access the resources they need.

Without a default gateway, your devices would have nowhere to send network traffic, and therefore, they would be unable to access the internet or other external network resources.

Conclusion

In conclusion, the default gateway plays a crucial role in network communication. It acts as a bridge between networks and ensures that devices can communicate and access external resources.

Linux users can view, add, and delete default gateways using commands or graphical interfaces. Wireless routers are usually considered as default gateways in home networks, and they provide internet access to all devices connected to them.

Default gateways eliminate the need for manual routing configurations and make network connectivity seamless and efficient.

Automatic Route Addition and Deletion

In the world of computer networks, it’s not uncommon for network administrators to add and delete routes automatically, without manual intervention. This can be useful in various scenarios, such as when a new network interface is added, or when a secondary backup link is configured.

In this section, we’ll explore the possible scenarios of automatic route addition and deletion, as well as how to isolate the default route from the configured routes using the Grep command. Possible Scenarios of

Automatic Route Addition and Deletion

Automatic route addition and deletion can occur in a variety of scenarios.

For example, when a new network interface is added to a system, the system assigns a new IP address to the interface, along with a corresponding subnet mask. This new network interface requires a default gateway to communicate outside the local network.

The system can automatically add a default gateway for the new interface without manual intervention. Another scenario where automatic route addition and deletion can happen is when a network link goes down, and the system needs to switch to a backup link.

In such a case, the network administrator can configure the system to automatically add the new route and remove the old route without manual intervention.

Isolating the Default Route from Configured Routes using Grep Command

It’s essential to be able to isolate the default route from the configured routes, especially if you want to modify the default route. You can use the Grep command to filter out the default route from the configured routes.

Here’s how you can do it:

First, run the following command to view the current routing table:

sudo ip route show

You’ll see a list of each network route and its corresponding destination network, subnet mask, default gateway, and interface. Next, use the Grep command to isolate the default route from the configured routes using the following syntax:

sudo ip route | grep default

This command will display the default gateway and its corresponding interface.

Making Changes Permanent

After making changes to the routing table, it’s crucial to make these changes permanent. This ensures that the changes persist even after a system reboot.

In this section, we’ll explore how to alter configuration files to make changes permanent, how to use the Netplan command to apply changes, and how to test changes with the Netplan Try option.

Altering Configuration Files to Make Changes Permanent

The easiest way to make changes permanent is to alter configuration files. In Linux, the configuration files for network settings are located in the /etc/network/ directory.

For example, if you want to add a new route to the routing table permanently, you can add the following line of code to the /etc/network/interfaces file:

up route add -net X.X.X.X netmask X.X.X.X gw X.X.X.X

Replace the Xs in this code with the actual IP address, subnet mask, and gateway address you want to add.

Using Netplan Command to Apply Changes

Netplan is a YAML-based tool that simplifies the process of managing network configurations in Linux. Here’s how you can use Netplan to apply changes to network settings:

sudo nano /etc/netplan/01-network-manager-all.yaml

This command will open the Netplan configuration file in Nano text editor.

You can then add the following code snippet to the file:

network:

ethernets:

ens33:

addresses: [192.168.10.10/24]

gateway4: 192.168.10.1

version: 2

In the above code, “ens33” represents the name of your network interface card. Replace “192.168.10.10” with the IP address you want to assign to your Linux system and replace “192.168.10.1” with the IP address of your default gateway.

Testing Changes with Netplan Try Option

To test changes made with Netplan, you can use the “Netplan Try” option. This option allows you to test configurations before applying them permanently.

Once you’ve made changes to the YAML file, run the following command:

sudo netplan try

This command loads the configuration for a five-minute timespan, allowing you to test the changes. If the changes work correctly, you can apply them permanently by running the following command:

sudo netplan apply

Conclusion

In conclusion, automatic route addition and deletion can be useful in various scenarios and can help simplify network administration tasks. It’s important to understand how to isolate the default route from the configured routes and make routing changes permanent to ensure that they persist across system reboots.

By altering configuration files and using tools like Netplan, network administrators can make network configuration changes more efficient and effective. The Netplan Try option allows administrators to test configurations before applying them, thereby avoiding any potential issues and minimizing downtime.

Specifics for Ubuntu 20.04 System

Ubuntu is one of the most popular Linux operating systems and is widely used in both personal and enterprise environments. In this section, we’ll explore the specifics of using Netplan command for Ubuntu and creating a new default gateway on the wlo1 interface for Ubuntu 20.04 systems.

Using Netplan Command for Ubuntu

Netplan has become the default tool for managing network settings in Ubuntu 20.04 systems. Netplan uses YAML-based configuration files to manage network settings, simplifying network administration tasks.

To use Netplan on Ubuntu 20.04, follow these steps:

Step 1: Open the Netplan configuration file

In a terminal window, open the Netplan configuration file by typing:

sudo nano /etc/netplan/01-netcfg.yaml

This command opens the Netplan configuration file in a text editor. Step 2: Edit the configuration file

To edit and customize the configuration file, add or modify network interface configurations within the file using the YAML format.

Step 3: Save and apply changes

After making changes to the configuration file, save the file by pressing Ctrl+O and then exit by pressing Ctrl+X. To apply changes to the network configuration, run the following command:

sudo netplan apply

Creating New Default Gateway on wlo1 Interface for Ubuntu

To create a new default gateway for the wlo1 interface on an Ubuntu 20.04 system, follow these steps:

Step 1: Identify the network interface

Identify the network interface for which you want to create a new default gateway. To do this, enter the following command in the terminal window:

ifconfig

The output will list all of the available network interfaces on your system.

Identify the interface you want to use and make note of its name. Step 2: Create a new YAML file

Create a new configuration file for the interface by entering the following command:

sudo nano /etc/netplan/99-custom.yaml

This command will open a new text editor.

Step 3: Add the new default gateway configuration

Add the new default gateway configuration to the new YAML file using the following syntax:

network:

version: 2

renderer: networkd

ethernets:

wlo1:

dhcp4: false

addresses: [192.168.1.123/24]

gateway4: 192.168.1.1

In the above code, “wlo1” represents the name of your network interface card. Replace “192.168.1.123” with the IP address you want to assign to your Linux system and replace “192.168.1.1” with the IP address of your default gateway.

Step 4: Save and apply changes

After adding the new default gateway configuration to the YAML file, save the file by pressing Ctrl+O and then exit by pressing Ctrl+X. To apply the changes to the network configuration, run the following command:

sudo netplan apply

Conclusion

Netplan is an easy-to-use tool for managing network settings on Ubuntu 20.04 systems. By creating a new default gateway on a specific interface like wlo1, you can enhance your network functionality and ensure smoother connectivity between your system and other devices.

The steps provided above are a simple and straightforward method to customize default gateway configurations on your Ubuntu 20.04 system. In conclusion, understanding and setting up the default gateway on Linux systems, specifically in Ubuntu 20.04, is crucial for efficient network communication.

By viewing, adding, and deleting default gateways using commands like IP and Route, network administrators can manage routes effectively. Altering configuration files and using tools like Netplan ensure that changes to the routing table are permanent and persist across system reboots.

Additionally, the ability to automate route addition and deletion, as well as isolate the default route using the Grep command, simplifies network administration tasks. It is important to remember that default gateways play a vital role in home networks, enabling easy navigation of the internet.

Overall, with a clear understanding of default gateways and their management, network administrators can ensure smooth and reliable network connectivity, facilitating efficient communication and access to resources.

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