Create KVM Network Bridge Ubuntu 22.04

In this post we will go through the process of creating a Bridged Networking adapter for Ubuntu 22.04.

Disable Netfilter

# vim /etc/sysctl.d/bridge.conf

Add the following lines then save and exit.

net.bridge.bridge-nf-call-ip6tables=0
net.bridge.bridge-nf-call-iptables=0
net.bridge.bridge-nf-call-arptables=0

Create /etc/udev/rules.d/99-bridge.rules and add the following line. Save and Exit.

ACTION=="add", SUBSYSTEM=="module", KERNEL=="br_netfilter", RUN+="/sbin/sysctl -p /etc/sysctl.d/bridge.conf"

Reboot for the changes to take effect.

Get Network Interface MAC address

We will need the MAC address of your NIC in order to correctly configure the network bridge.

# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: enp2s0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 14:cc:20:02:df:e7 brd ff:ff:ff:ff:ff:ff

The NIC we will attach the bridge to is enp2s0. The MAC address is listed just after link\ether.

14:cc:20:02:df:e7

Create Netplan configuration for the Bridge

Edit the /etc/netplan/00-installer-config.yaml file:

network:
  version: 2
  ethernets:
    enp2s0:
      dhcp4: false
      dhcp6: false
  bridges:
    br0:
      dhcp4: false
      dhcp6: false
      interfaces: [ enp2s0 ]
      macaddress: 14:cc:20:02:df:e7
      addresses: [192.168.1.200/24]
      nameservers:
         addresses: [8.8.8.8, 8.8.8.4]
      routes:
         - to: default
           via: 192.168.1.1
      mtu: 1500
      parameters:
        stp: true
        forward-delay: 4

Save and exit.

Apply the changes:

netplan apply

Add the bridge to KVM

Create a new file called bridge.xml with the following contents:

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

More information can be found about the libvirt XML format at libvirt documentation.

Run the following commands add the bridge to KVM:

sudo virsh
net-define /path/to/br0.xml
net-start br0
net-autostart br0
net-list
quit