[libvirt-users] How can I define a network using an exist host bridge

Hi all, When I defined a network use the host bridge "virbr1" an error occurred : "libvir: error : Unable to create bridge virbr1: File exists" But how can I define this network use the host bridge "virbr1" ? <network> <name>def1</name> <bridge name='virbr1'/> <forward mode='nat'> <interface dev='eth0'/> </forward> </network> Thanks, Kevin