Step by step factory reset of Cisco ASA 5500 series firewall

Step by step factory reset of Cisco ASA 5500 series firewall 

Connect your console cable and make sure you can see the command prompt for the ASA – even if you can’t log in. You will need to stop the boot process early on, so you don’t want to be messing about trying to get the console to work while it’s booting, or you’ll miss your prompt, and have to start again.

Power cycle the appliance – flick the power switch on the front off and on again.

Watch the boot progress, and when prompted, press Esc to interrupt the boot and enter ROM Monitor mode. you should now see the rommon prompt:

rommon #0>

Enter the confreg command to view the current Configuration Register setting:

rommon #0> confreg

The appliance will most probably have the default Configuration Register setting of 0x01. Answer no when it asks you if you want to change the Configuration Register setting.

Change the Configuration Register to 0x41, which causes the appliance to bypass its saved config at boot:

rommon #1> confreg 0x41

Reboot the appliance with the boot command:

rommon #2> boot

The appliance bypasses its startup configuration. When it finishes booting, you should see the default prompt:

ciscoasa>

Enter the enable command to enter Privileged Mode. The default password is blank, so when the appliance prompts you for a password, simply press return:

ciscoasa> enable

Erase the startup config by issuing the write erase command:

ciscoasa# write erase

Enter Configuration Mode:

ciscoasa# configure terminal

Reset the Configuration Register to the default of 0x01:

ciscoasa(config)# config-register 0x01

Exit from Configuration mode:

ciscoasa(config)# exit

Verify the Configuration Register settings by issuing the Show Version command:

ciscoasa# show version

At the bottom of the output, you should see the Configuration Register settings: Configuration register is 0x41 (will be 0x1 at next reload)

Save the settings by issuing the write command:

ciscoasa# write

Reboot the appliance:

ciscoasa# reload

When the appliance reboots, it will have a basic factory default configuration, with a blank password.

You can now proceed to configure the firewall as necessary.