I'm not sure. You sure you can't find out who set up your network? If not you could try to contact the manufacturer and they would be able to tell you quite easily.External IP? So this is your WAN IP not your router LAN IP?Also, your network map isn't exactly clear. Does it go:Internet cable -- Ambit -- Lynksys -- Laptop \ DesktopIs this because the Ambit only has the one ethernet port and no wireless function?Have you tried basic passwords like 1111 or 1234 or 9999? These sometimes work.