Before i forget Gnome Boxes Network Bridge

Often after an fresh OS Install in an Gnome Virtual Box the network stops or is restricted to the local machine for no obvious reason.

virsh -c qemu:///session list --all

lists all the actual installed machines

virsh edit machinename

edits the settings of the virtual gnome boxes machine

Inn the settings we are looking for something like this

<interface type='user'>
 <mac address='52:54:00:bf:c5:97'/>
 <model type='rtl8139'/>
 <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
</interface>

and replace it with the following

<interface type='bridge'>
 <mac address='00:16:3e:1a:b3:4a'/>
 <source bridge='virbr0'/>
 <model type='virtio'/>
 <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
</interface>

if it doesn't work after a restart.
we have to edit additionally the following file /etc/qemu/bridge.conf
that it contains the following line

allow virbr0