[libvirt] libvirt: use existing network bridge

Hi, I met a problem setting up virt-manager and libvirt: I want to use an existing customized network bridge with libvirt (I need special iptables rules and a custom DHCP setup). So I created a network definition file like this: <network> <name>NAT</name> <bridge name='br-nat' /> </network> Unfortunately, I'm unable to activate this network, because libvirt tries to create the bridge `br-nat' and fails, because it already exists: # virsh net-start NAT error: Failed to start network NAT error: cannot create bridge 'br-nat': File exists I just want libvirt to attach the guest's tap devices to this existing bridge. I don't want libvirt to manage the network. Is there any chance to realize this set-up? It should work with virt-manager using the graphical wizard. Thanks! Regards Sascha