openstack about linux bridge? i'm confused

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http://askubuntu.com – all Thanks in advance,i'm confused for few days. i deployed openstack folsom release(with nova-network not quantum) in ubuntu 12.04 and create two private network via "nova-manage network create private .......",so i created two bridges br100 and br200, then i boot two vms with two network card(eth0 and eth1) ok, then i will do something in the vms,i create br001 and add interface eth1 into br001 in vmA and vmB,and add ips to br001,the ips are in the same network. The TOPOLOGY is below: DELL SERVER | br100(vnet0&vnet2) | br200(vnet1&vnet3) vmA | eth0( | eth1(172.20.2 (HowTos)