[libvirt-users] simulate "network cable unplugged"

Hi All, Using the virt-manager/libvirtd/qemu-kvm stack (centos 6), is it possible to leave a NIC "installed" but cause it to simulate that the network cable is unplugged? Preferably this could be "hot" plugged/unplugged but otherwise doing it cold. Guest os is also centos 6, in case it matters (shouldn't). Any pointers? Thanks, David Mansfield Cobite, INC.