My home network is serviced by an ADSL line. The modem is in bridged mode. The router performs the PPPoE.

Three computers are connected to the router: two wired Windows 7 boxes and a Ubuntu Linux box over wifi.

The computers are hosting various forms of services including FTP and HTTP. The router has port forwarding mapped from the relevant ports to the reserved IP addresses for the computers.

If I attempt to connect to a server inside the network, such as ftp://67.xx.xxx.xxx from inside the network, the request times out. However if I connect using the internally mapped address, such as ftp://192.168.0.100, all is well.

This is a nuisance for setting up software, especially on the laptop which needs to be able to phone home from anywhere, and I just don't have enough expertise with networking to know why this is occurring to even have a clue whether it can be solved or not.

edit: It should be noted that the servers can be accessible outside the network - say, at the starbucks across the street - perfectly fine, using the ISP provided address and the appropriate port.