I found something strange I can't solve by myself. Sometimes I getting configuration where VMs traffic get to the gre tunnes via following sequence: tap->qbr->qvb->qvo->br-int->br-tun->eth0. It described here: http://docs.openstack.org/grizzly/openstack-network/admin/content/under_the_hood_openvswitch.html But sometimes I getting very different configuration: tap->br-int->br-tun->eth0. It working, and working fine. And I just can't find option or configuration difference, or combination of both which cause switching between 'simple' and 'normal' scheme. I feel like I don't understand something basic and something important. Any ideas? Thanks!