Recently replaced my RTA-1320 (stupid thing lasted 2 years and then was dropping connections every 2 mins) with a TP-Link 8840.  Connection wise its rock solid and a great little unit ... BUT :)

Ive got a Small Business Server sitting behind the ADSL modem ... and on the Router I just open up some required ports for me to access, eg Mail and FTP etc. It all works but Ive got an issue with restricting access at the Router and even in SBS.

When an access is made from the Internet to my Server, it used to log the External IP Address of the remote host which made it very easy to only allow specific IP Address access and restrict relaying etc.  Now everything accessing is showing the internal IP Address of the ADSL modem.

Is there someway to change this behaviour?  Wouldnt be so bad, but Ive managed to find out from the TP-Link support that IP Filtering doesnt work in my current setup:

"With regard to the IP filtering rules, all incoming traffic will only be blocked when the unit’s firewall has been enabled. However, enabling/disabling this setting is only available on the TD-8840 when it has been configured to use MAC Encapsulation Routing (MER) or IP over ATM (IPoA) connection mode in its ATM PVC Configuration page when configuring a connection under Advanced Setup -> WAN.

Im guessing those options arent available in NZ?