The flash procedure is quite simple. Just use the DIR-880L web admin portal to flash the web flash bin file.
It works, but it is not as good as the original factory ROM.
Two problems I found.
The WiFi signal is not as strong as old one. No WiFI at some rooms.
It is not as stable as before. Sometimes the connection is lost.
Then, I think it is time to flash the original ROM.
The best way to revert install the original firmware to D-Link DIR-880L
1. Disconnect the power to router
2. Set IP address to 192.168.0.10
3. Connect computer via ethernet to LAN 1 (I’ve also disconnected from all wireless networks)
4. Hold reset with a pen and while holding reset, plug in the power
5. Power LED should now be flashing orange and LAN 1 solid green after 5-15 seconds
6. Then browse to 192.168.0.1 to be greeted by the emergency room (I use Chrome if that matters)
Then flash the bin file above. All the D-Link stuff come back.
The story is starting from IPv6. I want to use HE.Net ipv6 channel broker service. It needs to ping my ipv4 address. But D-Link DIR-880L does not the response the ICMP. It disabled the function and can not change it from the web admin interface. The old version of D-Link web admin has this kind of function. But the new version admin web interface has blocked it by default.
I think DD-WRT firmware has a lot of features and can almost change anything of the router. That is the main reason I flashed the DD-WRT firmware on DIR-880L.
But the most important is the connection ability and stability. So, now my router is using the latest factory firmware.