TranslateProject/sources/tech/20180128 How to add network bridge with nmcli (NetworkManager) on Linux.md

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: Another option is to type the following command:

$ nmcli con show
$ nmcli connection show --active 

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

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 to view the IP settings:

$ ip a s
$ ip a s br0

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: $ cat /tmp/br0.xml Append the following code:

<network>
  <name>br0</name>
  <forward mode="bridge"/>
  <bridge name="br0" />
</network>

Run virsh command as follows:

# virsh net-define /tmp/br0.xml
# virsh net-start br0
# virsh net-autostart br0
# virsh net-list --all

Sample outputs:

 Name State Autostart Persistent
----------------------------------------------------------
 br0 active yes yes
 default inactive no yes

For more info read the following man page:

$ man ip
$ man nmcli

about the author

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, Facebook, Google+.

---

via: https://www.cyberciti.biz/faq/how-to-add-network-bridge-with-nmcli-networkmanager-on-linux/

作者：Vivek Gite 译者：译者ID 校对：校对者ID

本文由 LCTT 原创编译，Linux中国 荣誉推出