Password reset for 820 & 830 series routers

You'll need a Cisco console cable (aka a config cable or blue rollover cable) for this. Attach the cable to a serial port on a computer that has a terminal program such as Hyperterminal (Windows) or Terminal (OSX) on it. You'll need to connect at 9600bps 8n1 (8 data bits, 1 stop bit, no parity) and no flow control.

If the router is currently powered up, you should be able to get something back from the device if you hit enter - likely a password prompt. Alternatively, if may give you a command prompt, but trying to change level (entering the enable command) will prompt for a password. If this is the case, then read on to reset these passwords.

Switch the router off (power off) and back on again. Send a break command within the first minute of power being restored. This will take the router to ROMMON.

In this state, you should see a prompt saying rommon 1> . The 1 will increment each time you hit enter on your keyboard.

Type: confreg 0x2142 [enter]

Type: reset [enter]

The router will now reboot, but the saved configuration won't be loaded this time around. Because of this, you'll be asked if you want to set the router up. Enter no [enter] for each question, until you get to the Router> prompt.

Type: enable [enter]

The prompt should now change to Router# indicating that you're in the privileged mode.

At this stage, you've got the choice of overwriting the existing configuration entirely. You should only do this if you're sure that you don't need to retain any of the existing settings. If you're sure you want to do this, simply type copy running-config startup-config [enter]. You should then change the config-register back (we changed this at the rommon prompt earlier). To do this, type config-register 0x2102 [enter]. You can now reset the router by typing exit [enter] then reset [enter]. The first exit is needed to exit the configuration mode.

If, instead, you'd like to merely reset the passwords, then type conf t [enter]. This places the router into configuration mode. Next, type enable secret [enter]. Where is the new password you wish to use to access the privileged state. If you were prompted for a password when you connected the console cable earlier on, you can reset this by typing line con 0 [enter] no password [enter]. From here, type exit [enter] exit [enter] then wr mem [enter]. The first exit is needed to exit the line con 0 configuration. The next one leaves the configuration mode, then the next command commits the configuration to memory.