Sorry for the late reply. See my inline response below:
>What Firmware version is currently loaded? Found on the routers web page under status.
Firmware is 1.20B01 for A1 hardware
>What region are you located?
Southeast Asia
>Internet Service Provider and Modem Configurations
>What ISP Service do you have? Cable or DSL?
DSL
>What ISP Modem Mfr. and model # do you have?
Baudtec rn243r4
>Is ISP Modem/Service using Dynamic or Static WAN IP addressing?
Dynamic WAN IP
>Check ISP MTU requirements, Cable is usually 1500, DSL is around 1492 down to 1472. Call the ISP and ask. Link>Checking MTU Values
Checking from ping unfragmented is 1492
>For DSL/PPPoE connections on the router, ensure that "Always ON" option is enabled.
Not applicable
>If the ISP modem has a built in router, it's best to bridge the modem. Having 2 routers on the same line can cause connection problems: Link>Double NAT and >How NAT Works. Call the ISP and ask to see if the ISP modem can be bridged. To tell if the modem is bridged or not, look at the routers web page, >Status/Device Info/Wan Section, if there is a 192.168.0.# address in the WAN IP address field, then the modem is not bridged. If the modem can't be bridged >then see if the modem has a DMZ option and input the IP address the router gets from the modem and put that into the modems DMZ. Also check the routers >DHCP IP address maybe conflicting with the ISP modems IP address of 192.168.0.1. Check to see if this is the same on the ISP modem, and if modem can't be >bridged, change the DIR router to 192.168.1.1 or .0.254.
>Example of a D-Link router configured for PPPoE with ISP Modem bridged: PPPoE Configuration on a Router
The reason I want to bridge the DSL modem is to avoid the double NAT. How can I confirm if bridge mode is working where there is no WAN IP? I've disabled the DCHP server mode of DSL modem so I can't check its admin UI unless I make my LAN connected PC to static IP with the same subnet.
>Try the modem in router mode and the 880L in the modems DMZ if it has this feature...
If I do this, modem will become 1483MER, not 1483 bridge mode?