Follow the steps below to successfully Factory reset your Cisco IP phone:
- Unplug the power cable from the ip phone and then plug it back in.
- While the phone is powering up, and before the Speaker button flashes on and off, press and hold the hash # key.
- Continue to hold # until each line button (right of the LCD screen) flashes on and off in sequence in orange color.
- Now release the hash # key and type the following sequence 123456789*0#
After the sequence has been entered the line buttons on the phone flash orange, then green and the phone goes through the factory reset process. This process can take several minutes and the firmware of the IP Phone will be erased.