Including following steps:
b. Run "cloudstack-agent-upgrade". This script will upgrade all the existing bridge name to new bridge name, and update related firewall rules.
c. install a libvirt hook:
c1. mkdir /etc/libvirt/hooks
c2. cp /usr/share/cloudstack-agent/lib/libvirtqemuhook /etc/libvirt/hooks/qemu
c3. chmod +x /etc/libvirt/hooks/qemu
c4. service libvirtd restart