pix is not designed to handle such scenario.
usually a router is connected to the pix interface, which in turns connected to the internet.
e.g.
www <--> router a <--> pix outside interface
www <--> router b <--> pix intf2 interface
pix is not able to determine whether the internet link is active or not. the reason being the routers and the pix is directly connected, thus the link would never go down, regardless the internet link status on the other side of the router.
