Gaining Access when the AAA Server is Down
If the AAA server is down, you can access the PIX by entering the Telnet password initially, then pix for the username, and then the enable password (enable password whatever) for the password. If enable password whatever is not in the PIX configuration, enter pix for the username and press Enter. If the enable password is set but not known, you will need a password recovery disk to reset the password.
Password Recovery and AAA Configuration Recovery Procedure
Hope that helps.