How to create a Network Bridge on CentOS 7 / RHEL 7

Sometimes you may need to create network bridge adapter in Linux; specially during the settings of KVM (Kernel-based virtual Machine), and, also while setting up Linux system bins.

This bridge network allows virtual machines to have access to the external network and vice-versa, follow this guide to create network bridge on CentOS 7 / RHEL7.

A bridge interface is actually a virtual interface handled by a config file on your Linux system. Creating a bridge is quite simple, just follow those steps and you’re all set!

Install Module:

CentOS 7 comes with bridging module loaded on system boot by default, verify it by using below command.

# modinfo bridge
filename: /lib/modules/3.10.0-327.el7.x86_64/kernel/net/bridge/bridge.ko

If the module is not loading, you can load it using the following command:

# modprobe --first-time bridge

Install bridge-utils for controlling the network adapters.

# yum install bridge-utils -y

Create a Network Bridge:

Now its time To create a network bridge, create a file called “ifcfg-virbrN” replacing “N” with a number, such as “0” in the “/etc/sysconfig/network-scripts/“.

File doesn’t needs to be “virbrN“, you can also give a name like “brN”

# nano /etc/sysconfig/network-scripts/ifcfg-virbr0

Place the following content into that file, modify it according to your environment.

DEVICE="virbr0"
BOOTPROTO="static"
IPADDR="192.168.12.10"
NETMASK="255.255.255.0"
GATEWAY="192.168.12.2"
DNS1=192.168.12.2
ONBOOT="yes"
TYPE="Bridge"
NM_CONTROLLED="no"

Now, it’s the time to modify the network configuration of the existing adapter in such a way that it points to a bridge interface.

# nano /etc/sysconfig/network-scripts/ifcfg-eto16886627

Place the content like below.

DEVICE=eto16886627
TYPE=Ethernet
BOOTPROTO=none
ONBOOT=yes
NM_CONTROLLED=no
BRIDGE=virbr0

Restart the network using the following command.

# systemctl restart network

Use ifconfig command to see interface details.

# ifconfig

That’s all you have to do, Please Give your opinion below if you experience any issues or to discuss your ideas and experiences.

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