UPDATE: I just clarified with my friend, he actually meant, the traffic will be passed through from the LAN to WAN port, it's specific to device, in our case it's the Symantec Web Gateway Appliance. Now it's that true?
Original: If a cross cable is used to connect from an device to another, say firewall to a web gateway. When the web gateway is down (switched off, but cable still connected), the traffic sent to the web gateway will be "routed" back to firewall (maybe like a loopback?). But it won't for a straight cable.
I've heard about this from a friend, but I don't quite believe it, so I wanted to see if anyone else have heard about it.
EDIT: Yes, no traffic is transported by the controller or onboard MAC, but could the PHY be "shorted" electronically, TX shorted to RX, so data just looped over? Maybe it's an undocumented "feature" of some devices?