How to add network bridge with nmcli (NetworkManager) on Linux
======
I am using Debian Linux 9 "stretch" on the desktop. I would like to create network bridge with NetworkManager. But, I am unable to find the option to add br0. How can I create or add network bridge with nmcli for NetworkManager on Linux?
A bridge is nothing but a device which joins two local networks into one network. It works at the data link layer, i.e., layer 2 of the OSI model. Network bridge often used with virtualization and other software. Disabling NetworkManager for a simple bridge especially on Linux Laptop/desktop doesn't make any sense. The nmcli tool can create Persistent bridge configuration without editing any files. **This page shows how to create a bridge interface using the Network Manager command line tool called nmcli**.
### How to create/add network bridge with nmcli
The procedure to add a bridge interface on Linux is as follows when you want to use Network Manager:
1. Open the Terminal app
2. Get info about the current connection:
```
nmcli con show
```
3. Add a new bridge:
```
nmcli con add type bridge ifname br0
```
4. Create a slave interface:
```
nmcli con add type bridge-slave ifname eno1 master br0
```
5. Turn on br0:
```
nmcli con up br0
```
Let us see how to create a bridge, named br0 in details.
### Get current network config
You can view connection from the Network Manager GUI in settings:
[![Getting Network Info on Linux][1]][1]
Another option is to type the following command:
```
$ nmcli con show
$ nmcli connection show --active
```
[![View the connections with nmcli][2]][2]
I have a "Wired connection 1" which uses the eno1 Ethernet interface. My system has a VPN interface too. I am going to setup a bridge interface named br0 and add, (or enslave) an interface to eno1.
### How to create a bridge, named br0
```
$ sudo nmcli con add ifname br0 type bridge con-name br0
$ sudo nmcli con add type bridge-slave ifname eno1 master br0
$ nmcli connection show
```
[![Create bridge interface using nmcli on Linux][3]][3]
You can disable STP too:
```
$ sudo nmcli con modify br0 bridge.stp no
$ nmcli con show
$ nmcli -f bridge con show br0
```
The last command shows the bridge settings including disabled STP:
```
bridge.mac-address: --
bridge.stp: no
bridge.priority: 32768
bridge.forward-delay: 15
bridge.hello-time: 2
bridge.max-age: 20
bridge.ageing-time: 300
bridge.multicast-snooping: yes
```
### How to turn on bridge interface
You must turn off "Wired connection 1" and turn on br0:
```
$ sudo nmcli con down "Wired connection 1"
$ sudo nmcli con up br0
$ nmcli con show
```
Use [ip command][4] to view the IP settings:
```
$ ip a s
$ ip a s br0
```
[![Build a network bridge with nmcli on Linux][5]][5]
### Optional: How to use br0 with KVM
Now you can connect VMs (virtual machine) created with KVM/VirtualBox/VMware workstation to a network directly without using NAT. Create a file named br0.xml for KVM using vi command or [cat command][6]:
The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on [Twitter][7], [Facebook][8], [Google+][9].
