This is mainly for myself to remember how I did it. Might be helpful for others as well.

Install bridge-utils#

The bridge-utils are needed to configure a bridge.

apt install bridge-utils

Configure the bridge interface with DHCP#

Check with the following command which interface your physical interface is

ip -f inet a s

Mine is enp1s0

Create the file /etc/network/interfaces.d/br0. I prefer using DHCP over a static configuration. It allows me to configure everything on my DHCP server.

## DHCP ip config file for br0 ##
auto br0

# Bridge setup
 iface br0 inet dhcp
    bridge_ports enp1s0

Restart the network

systemctl restart networking

Configure interface for KVM#

Create a xml file, e.g. host-bridge.xml

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

Execute the following commands to configure the interface for KVM

virsh net-define host-bridge.xml
virsh net-start host-bridge
virsh net-autostart host-bridge

Firewall#

Allow all traffic on bridge interface

firewall-cmd --add-interface br0 --zone=trusted --permanent
firewall-cmd --reload