[libvirt] IPs via DHCP for guest domains

I'm curious to know how you are providing IPs for your Windows VMs when connected via a bridge. Since broadcasts from the VMs are going out the bridged interface, I'm thinking about implementing ebtables to block dhcp broadcasts from going in/out the interface so that dnsmasq would only respond to dhcp requests from the local guest VMs. Before I venture down this path, I thought I might ask if there's an easier way to do this with libvirt. Thanks for any help.