3 Ways to Create a Network Bridge in RHEL CentOS 8

A network bridge is a software component that allows multiple networks to be connected together, creating a larger network that can be used to share resources and communicate between devices. In Red Hat Enterprise Linux (RHEL) and CentOS 8, network bridging can be achieved in several ways, depending on your needs and preferences.

In this article, we will explore three primary methods to create a network bridge in RHEL/CentOS 8, using examples and step-by-step instructions. Whether you need to connect virtual machines or physical devices, these methods will help you set up a bridge that meets your requirements.

Method 1: Using nmcli Command Line Tool

The nmcli command line tool is a powerful utility for managing network connections in RHEL/CentOS 8. It can be used to create, modify, and delete network connections, including network bridges.

Step 1 Check Network Interfaces

Before creating a network bridge, you need to identify network interfaces that you want to bridge. Use the following command to list all available network interfaces on your system

nmcli device status

This command will show a list of network interfaces, along with their connection status and device type.

Step 2 Create a New Bridge Connection

To create a new bridge connection, use the following command

sudo nmcli connection add type bridge ifname br0

This command creates a new bridge connection with the name br0. You can replace br0 with any name you prefer.

Step 3 Add Network Interfaces to Bridge

To add network interfaces to the bridge, use the following command

sudo nmcli connection add type bridge-slave ifname eth0 master br0

Replace eth0 with the name of the network interface you want to add to the bridge. You can add multiple network interfaces by running this command multiple times with different interface names.

Step 4 Activate Bridge Connection

To activate the bridge connection, use the following command

sudo nmcli connection up br0

This command will bring up the bridge connection and activate it. Now, any device connected to network interfaces that you added to the bridge will be able to communicate with other devices on the same network.

Method 2: Using NetworkManager GUI

If you prefer a graphical user interface (GUI) over command line, you can use NetworkManager GUI to create a network bridge in RHEL/CentOS 8.

Step 1 Open NetworkManager GUI

Open NetworkManager GUI by clicking on the network icon in the system tray, then selecting Network Settings option.

Step 2 Create a New Bridge Connection

In NetworkManager GUI, click on the + button to add a new connection. Select Bridge option and click Create.

Step 3 Configure Bridge Connection

In the bridge connection settings, give the bridge a name (such as br0) and select network interfaces that you want to add to the bridge. You can also configure other settings, such as IP address and DNS servers, if needed.

Step 4 Activate Bridge Connection

Click on the toggle button to activate the bridge connection. Now, any device connected to network interfaces that you added to the bridge will be able to communicate with other devices on the same network.

Method 3: Using Network Scripts (Legacy Method)

Another way to create a network bridge in RHEL/CentOS 8 is by using network-scripts. This method involves manually editing configuration files to create a bridge and assign network interfaces to it. While it provides greater control over bridge configuration, it's considered a legacy approach.

Step 1 Install Bridge Utilities

Before creating a bridge using network-scripts, you need to install the bridge-utils package

sudo dnf install bridge-utils

Step 2 Create Bridge Configuration File

Create a new ifcfg file for the bridge

sudo vi /etc/sysconfig/network-scripts/ifcfg-br0

Add the following configuration

DEVICE=br0
TYPE=Bridge
BOOTPROTO=static
IPADDR=192.168.1.100
NETMASK=255.255.255.0
GATEWAY=192.168.1.1
ONBOOT=yes

Replace the IP address, netmask, and gateway with values appropriate for your network.

Step 3 Configure Network Interfaces

Edit the network interface configuration files to assign them to the bridge. For example, to bridge eth0

sudo vi /etc/sysconfig/network-scripts/ifcfg-eth0

Add the following lines

DEVICE=eth0
ONBOOT=yes
BRIDGE=br0

Step 4 Restart NetworkManager Service

After editing the configuration files, restart the NetworkManager service to apply changes

sudo systemctl restart NetworkManager.service

Verify the bridge status using

sudo brctl show

Comparison of Methods

Conclusion

Creating a network bridge in RHEL/CentOS 8 can be accomplished through multiple methods, each suited for different user preferences and requirements. The nmcli tool offers the best balance of power and simplicity, while NetworkManager GUI provides an intuitive interface for desktop users. Choose the method that best fits your environment and technical expertise.