Select
Link State Pass Through
if you want the
firewall to function transparently. When the firewall detects a link
down state for a link of the virtual wire, it brings down the other
interface in the virtual wire pair. Thus, devices on both sides of the
firewall see a consistent link state, as if there were no firewall
between them. If you don’t select this option, link status isn’t
propagated across the virtual wire.