I needed to get the PPPoE account off a router once (My boss didn't remember the router's admin password), so I connected the WAN port to my laptop and captured

I needed to get the PPPoE account off a router once (My boss didn't remember the router's admin password), so I connected the WAN port to my laptop and captured the PPPoE packets. I might have had to use a second ethernet port (USB hub with eth port) to allow the old router to talk to the telcom modem. Just bridge the two ports and capture the traffic.