...Incoming burst...

First, create an xml file containing the description of your network interface and the network (e.g. 10.0.0.0/24) it will manage:

<network>
  <name>vmbr0</name>
  <bridge name="vmbr0"/>
  <forward/>
  <ip address="10.0.0.1" netmask="255.255.255.0">
    <dhcp>
      <range start="10.0.0.193" end="10.0.0.254"/>
    </dhcp>
  </ip>
</network>

Notice we configured a dhcp. This will the host to act as a DHCP server on that interface and provide leases on the range of address provided.

If you are wondering about identifiers (i.e. uuid) and MAC addresses, you can leave that up to libvirt.

Then place this file vmbr0.xml in libvirt’s folder containing qemu networks. In Debian you would find it by default at /etc/libvirt/qemu/networks/.

cp vmbr0.xml /etc/libvirt/qemu/networks/

Define your virtual network interface:

cd /etc/libvirt/qemu/networks/
virsh net-define vmbr0.xml

You can now edit it further if you wish. In the future, be careful to only use this command to edit it:

virsh net-edit vmbr0

Start it:

virsh net-start vmbr0

To have it starting automatically at boot:

virsh net-autostart vmbr0

Congratulations, you now have a virtual network and an interface that you can connect your virtual machines to!

...Sent by Lazy Monkey...