Cisco Official Documentation Notes:
To recover from the loss of passwords, perform the following steps:
Step 1 Connect to the Security Appliance console port by Super Terminal
Step 2 Power off the security appliance, and then power it on.
Step 3 During The startup messages, press the Escape key when prompted to enter ROMMON.
Step 4 To set the security appliance to ignore the startup configuration at reload, enter the following command:
Rommon #1 > Confreg ( 0x41) in Rommon mode to change the value of: 0x41, restart the device by boot)
The security appliance displays the current configuration register value, and asks if you want to change
The value:
Current Configuration register:0x00000011
Configuration Summary:
Boot TFTP image, boot default image from Flash on netboot failure
Do I wish to change this configuration? y/n [n]:
Step 5 Record Your current configuration register value, so you can restore it later.
Step 6 at the prompt, enter Y to change the value.
The security appliance prompts for new values.
Step 7 Accept The default values for all settings, except for the "Disable system configuration?" VALUE; At that
prompt, enter Y.
Step 8 Reload The security appliance by entering the following command:
Rommon #2 > Boot
The security appliance loads a default configuration instead of the startup configuration.
Step 9 Enter Privileged EXEC mode by entering the following command:
Hostname> Enable
Step Ten when prompted for the password, press Return.
The password is blank.
Step one Load the startup configuration by entering the following command:
hostname# Copy Startup-config Running-config
Step Enter Global configuration mode by entering the following command:
hostname# Configure terminal
Step passwords in the configuration by entering the following commands, as necessary:
Hostname (config) # password Cisco (config password)
Hostname (config) # enable password Cisco (configure enable password)
Hostname (config) # username name password Cisco (configure users and Passwords)
Step Change the configuration register to load the startup configuration at the next reload by entering the
Following command:
Hostname (config) # config-register value (change back to register value: 0x11)
Where value is the configuration register value of noted in Step 5. 0x1 is the default configuration
Register.
Step Save The new passwords to the startup configuration by entering the following command:
Hostname (config) # copy running-config startup-config (save config reboot to recover password)
That's a completely procedure of restoring lost password on ASA5500 security appliance.
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Cisco ASA5505 Password Recovery