Here is the interesting part most blogs don't tell you:
A: IN_2.12 (or newer). Older versions drop the VCI/VLAN 100 configuration after every reboot. D-link Dsl-2750u V2 Latest Firmware Update
The big headline here is the fix for (and several other undisclosed buffer overflow vulnerabilities). In layman's terms: Hackers have been scanning for old DSL-2750u units to take control of them without a password. This update closes that backdoor. Here is the interesting part most blogs don't