Create Network Bridge for multipass on Ubuntu

11 minute read

A network bridge is nothing but a device that joins two local networks into one network. It works at the data link layer (layer 2 of the OSI model). Network bridges often used with virtualization software. For example, popular software such as KVM, LXD, or Docker users can configure bridges instead of NAT-based networking. The nmcli command-line tool can create a 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 on an Ubuntu 20.04 LTS Linux server. Tutorial requirements Requirements Ubuntu 18.04/20.04 LTS server Root privileges Yes Difficulty level Easy Est. reading time 5 minutes

Table of contents ↓

Adding network bridge
Prerequisite
Creating a Linux network bridge
Disable or enable STP
Set up static or DHCP based IP address
Enable br0 network bridge interface
Verification network bridge
Conclusion

Advertisement Ubuntu 20.04 add network bridge (br0) with nmcli

The procedure to create and add a bridge interface on Ubuntu version 20.04 is as follows when you want to use Network Manager:

Open the Terminal app or log in using the ssh command
Find out information about the current Ubuntu network connection:
sudo nmcli con show
Then, add a new bridge called br0:
sudo nmcli con add ifname br0 type bridge con-name br0
Create a slave interface for br0 using enp0s31f6 NIC:
sudo nmcli con add type bridge-slave ifname enp0s31f6 master br0
Turn on br0 interface to get an IP via DHCP:
sudo nmcli con up br0
Static IP settings are discussed below for the br0 interface

Let us see all examples and instructions in detail to create a network bridge in Ubuntu Linux version 20.04 LTS server. Prerequisite for creating a Linux network bridge on Ubuntu 20.04

First thing, obtain information about the current Ubuntu Linux interface and IP address as we need this information later. Hence, type the following commands: $ nmcli con show $ nmcli connection show –active

Outputs:

NAME UUID TYPE DEVICE ETH0 71a189f2-9cb9-49f0-8464-37a6801740e3 ethernet enp0s31f6

So my server has an “ETH0” which uses the enp0s31f6 Ethernet interface. I am going to set up a bridge interface named br0 and add (enslave) an interface to enp0s31f6. Step 1 – Creating a network bridge named br0

The syntax is: $

$ sudo nmcli con add type bridge-slave ifname enp0s31f6 master br0 $ nmcli connection show

Ubuntu 20.04 add network bridge (br0) with nmcli command Step 2 – Disable or enable STP for network bridge

The primary purpose of Spanning Tree Protocol (STP) is to ensure that you do not create loops when you have redundant paths in your network. We can disable STP or enable as follows for br0: $ sudo nmcli con modify br0 bridge.stp no

Ubuntu 20.04 Linux nmcli command to enable STP with br0

$ sudo nmcli con modify br0 bridge.stp yes

Verification

$ nmcli con show $ nmcli -f bridge con show br0

Outputs:

bridge.mac-address: – bridge.stp: yes bridge.priority: 32768 bridge.forward-delay: 15 bridge.hello-time: 2 bridge.max-age: 20 bridge.ageing-time: 300 bridge.group-forward-mask: 0 bridge.multicast-snooping: yes bridge.vlan-filtering: no bridge.vlan-default-pvid: 1 bridge.vlans: –

Step 3 – Set up static or DHCP based IP for network bridge interface

We have not allocated any static IP address to our br0 interface. Hence, if the DHCP server is available, it should provide IP addresses and other settings. For instance, we can grab IP settings using DHCP as follows: $ sudo nmcli con up br0 $ ip a s br0 $ ping www.cyberciti.biz

However, on servers, we typically set up a static IP address. In this example, I am converting existing enp0s31f6 IP network settings to br0 settings as follows: IPv4 br0 settings

$ sudo nmcli connection modify br0 ipv4.addresses ‘192.168.2.25/24’ $ sudo nmcli connection modify br0 ipv4.gateway ‘192.168.2.254’ $ sudo nmcli connection modify br0 ipv4.dns ‘192.168.2.254’ $ sudo nmcli connection modify br0 ipv4.dns-search ‘sweet.home’ $ sudo nmcli connection modify br0 ipv4.method manual IPv6 br0 settings

$ sudo nmcli connection modify bridge0 ipv6.addresses ‘Your-Static-IPv6-Address’ $ sudo nmcli connection modify br0 ipv6.gateway ‘Your-Static-IPv6-Gateway-Address’ $ sudo nmcli connection modify br0 ipv6.dns ‘Your-Static-IPv6-DNS’ $ sudo nmcli connection modify br0 ipv6.dns-search ‘sweet.home’ $ sudo nmcli connection modify br0 ipv6.method manual Step 4 – Enable br0 network bridge interface on Ubuntu Linux

So far, we configured required network settings. It is time to turn it on our br0: $ sudo nmcli con up br0 $ nmcli con show

Wait for some time to activate settings. Step 5 – Verification network bridge settings

Use the ip command to view the IP settings for br0 bridge on Ubuntu box: $ ip a s $ ip a s br0

You can remove enp0s31f6 as br0 got a static IP address itself as enp0s31f6 will be in forwarding state: $ sudo nmcli connection delete enp0s31f6

or

$ sudo nmcli connection delete ETH0

Here is how it looks using the ip command: $ nmcli connection show $ ip a show br0 $ nmcli device

interface active and works with br0

$ ip a show enp0s31f6 $ ip r

Check Internet and local LAN connectivity using ping command

$ ping -c 4 www.cyberciti.biz $ ping -c 4 192.168.2.25

Show the link status of Ethernet devices and bridge devices on Ubuntu Linux machine: $ ip link show master br0 $ bridge link show $ bridge link show dev enp0s31f6

Verify and Create a Network Bridge in Ubuntu 20.04 Linux LTS server Conclusion

In this tutorial, you learned how to add and create a Linux Network Bridge on Ubuntu 20.04 LTS server. See nmcli docs online for more info. This entry is 8 of 11 in the Linux and Unix Network Bridging Tutorial series. Keep reading the rest of the series:

Debian Linux: Configure Network Interfaces As A Bridge / Network Switch
OpenBSD: Configure Network Interface As A Bridge / Network Switch
How To PFSense Configure Network Interface As A Bridge / Network Switch
FreeBSD: NIC Bonding / Link Aggregation / Trunking / Link Failover
How To Setup Bridge (br0) Network on Ubuntu Linux 14.04 and 16.04 LTS
Ubuntu setup a bonding device and enslave eth0+eth2
Setup Bonded (bond0) and Bridged (br0) Networking On Ubuntu
Ubuntu 20.04 add network bridge (br0) with nmcli command
CentOS 8 add network bridge (br0) with nmcli command
How to add network bridge with nmcli (NetworkManager) on Linux
Set up and configure network bridge on Debian Linux

About the author: Vivek Gite is the founder of nixCraft, the oldest running blog about Linux and open source. He wrote more than 7k+ posts and helped numerous readers to master IT topics. Join the nixCraft community via RSS Feed, Email Newsletter or follow on Twitter.

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unixpro Aug 10, 2020 @ 0:33

I think there’s a limitation with the standard Linux bridge when working with wireless adapters. Actually I think it’s a limitation with wireless link layer then authentication and trying to bridge Ethernet layer 2 over that authenticated stack if you get me.
Reply Link
perli Aug 31, 2020 @ 15:00

Hi, i have trouble withe getting an ip from the DHCP server to the bridge while the vm does get an ip. i would appreciate if you explain how to activate the br to work with dhcp , not based on if my dhcp server works in general (I’m on wireless). Thanks
Reply Link
PavelN Oct 6, 2020 @ 12:25

BTW: you have a typo in commands (missing con-name option) :
> Then, add a new bridge called br0:
sudo nmcli con add type bridge ifname br0

later in the page there is a proper syntax including “con-name” :
sudo nmcli con add ifname br0 type bridge con-name br0
Reply Link
     Vivek Gite Oct 26, 2020 @ 12:59

    Fixed it. Thanks for the tip and I appreciate your feedback.
    Reply Link
InnocentBystander Jan 26, 2021 @ 4:35

What is exactly ‘sweet.home’ in
sudo nmcli connection modify br0 ipv4.dns-search 'sweet.home'

Where does this value come from and what is the purpose/usage of this setting?

Thanks
Reply Link
     Vivek Gite Jan 27, 2021 @ 19:36

    That is my own domain search name set up in my DHCPD. So instead of typing ssh ‘mylaptop.sweet.home’, I type ‘mylaptop’. You can ignore sudo nmcli connection modify br0 ipv4.dns-search ‘sweet.home’ if you don’t have such fancy config.
    Reply Link
Beau G Apr 8, 2021 @ 13:21

Hello, I am getting the following error:

sudo nmcli con up br0
Error: Connection activation failed: Connection 'br0' is not available on device br0 because device is strictly unmanaged

nmcli con show
NAME                 UUID                                  TYPE      DEVICE
br0                  61d76e77-f193-4aea-94b2-02128aa5e8f1  bridge    --
bridge-slave-enp3s0  810348e4-c676-42d1-80c1-0414ce956130  ethernet  --

I restarted network manager. Nothing gives.
Reply Link
    Gautham Apr 8, 2021 @ 15:09

    Look like br0 is in managed state.

    sudo nmcli dev set {interface} managed {option}

    Your {interface} name such as eth0/enp3s0/br0. And {option} can be false, no, off, on, true, and yes. Try something as follows:

    sudo nmcli dev set br0 managed yes

    Reply Link

Bob Liotta

Ubuntu 20.04 Linux nmcli command to enable STP with br0

Verification

or

interface active and works with br0

Check Internet and local LAN connectivity using ping command