the correct command one connected via telnet is: wan set service pppoe_ptm_875_2_d --protocol pppoe --nat disable where pppoe_ptm_875_2_d is the name of your pppoe connection (use wan show connection...

IMHO this is a web gui bug. The option is missing. TP-LINK please fix it. In the meanwhile you can disable the NAT through the telnet interface with the "wan" command.

I have solved this by connection with telnet and changing it with "wan" command on the specific service

Model : Hardware Version : Not Clear Firmware Version : ISP : When configuring a connection with PPPoE from the WEB GUI, NAT cannot be disabled (Enable NAT option not available). I have solved it...