[libvirt-users] bridge could not be initialized

Hi I'm trying to run VM using libvirt.xml file and getting following error... virsh start instance-00000003 error: Failed to start domain instance-00000003 error: internal error Process exited while reading console log output: failed to launch bridge helper kvm: -netdev bridge,br=qbr1f2191ce-38,id=hostnet0: Device 'bridge' could not be initialized Below is the libvirt.xml file.. domain type="kvm"> <uuid>d9f007b9-584f-41c8-a706-e096f354575b</uuid> <name>instance-00000003</name> <memory>524288</memory> <vcpu>1</vcpu> <os> <type>hvm</type> <kernel>/opt/stack/data/nova/instances/d9f007b9-584f-41c8-a706-e096f354575b/kernel</kernel> <initrd>/opt/stack/data/nova/instances/d9f007b9-584f-41c8-a706-e096f354575b/ramdisk</initrd> <cmdline>root=/dev/vda console=tty0 console=ttyS0</cmdline> </os> <features> <acpi/> <apic/> </features> <clock offset="utc"> <timer name="pit" tickpolicy="delay"/> <timer name="rtc" tickpolicy="catchup"/> </clock> <devices> <disk type="file" device="disk"> <driver name="qemu" type="qcow2" cache="none"/> <source file="/opt/stack/data/nova/instances/d9f007b9-584f-41c8-a706-e096f354575b/disk"/> <target bus="virtio" dev="vda"/> </disk> <interface type="bridge"> <mac address="fa:16:3e:26:55:ff"/> <model type="virtio"/> <source bridge="qbr1f2191ce-38"/> <target dev="tap1f2191ce-38"/> <filterref filter="nova-instance-instance-00000003-fa163e2655ff"/> </interface> <serial type="file"> <source path="/opt/stack/data/nova/instances/d9f007b9-584f-41c8-a706-e096f354575b/console.log"/> </serial> <serial type="pty"/> </devices> </domain> Please help regarding this. Thanks Abhishek Jain