Hard reset or 30/30/30
From DD-WRT Wiki
Hard Reset or 30/30/30 reset
- With the unit powered on, press and hold the reset button on back of unit for 30 seconds
- Without releasing the reset button, unplug the unit and hold reset for another 30 seconds
- Plug the unit back in STILL holding the reset button a final 30 seconds.
This will clear out the NVRAM and set the dd-wrt back to default values.
This procedure should be done BEFORE and AFTER every firmware upgrade/downgrade
Do not use configuration restore if you change firmware builds (different svn build numbers)