Saturday, March 21, 2009

Cisco: Password Recovery

Ever lost the password to a Cisco device? I've had to do this about 4 times so far during my career (Not because I lost the password personally!). The steps are similar for many Cisco devices. These are the steps to reset the enable password on an ASA5505 Security Appliance.

The following steps were designed using a Cisco ASA 5505 Security Appliance. They are not appropriate for a Cisco PIX Firewall appliance.

1. Power-cycle your security appliance by removing and re-inserting the power plug at the power strip.
2. When prompted, press Esc to interrupt the boot process and enter ROM Monitor mode. You should immediately see a rommon prompt (rommon #0>).
3. At the rommon prompt, enter the confreg command to view the current configuration register setting: rommon #0>confreg
4. The current configuration register should be the default of 0x01 (it will actually display as 0x00000001). The security appliance will ask if you want to make changes to the configuration register. Answer no when prompted.
5. You must change the configuration register to 0x41, which tells the appliance to ignore its saved (startup) configuration upon boot: rommon #1>confreg 0x41
6. Reset the appliance with the boot command: rommon #2>boot
7. Notice that the security appliance ignores its startup configuration during the boot process. When it finishes booting, you should see a generic User Mode prompt: ciscoasa>
8. Enter the enable command to enter Privileged Mode. When the appliance prompts you for a password, simply press (at this point, the password is blank): ciscoasa>enable Password: ciscoasa#
9. Copy the startup configuration file into the running configuration with the following command: ciscoasa#copy startup-config running-config Destination filename [running-config]?
10. The previously saved configuration is now the active configuration, but since the security appliance is already in Privileged Mode, privileged access is not disabled. Next, in configuration mode, enter the following command to change the Privileged Mode password to a known value (in this case, we'll use the password system): asa#conf t asa(config)#enable password system
11. While still in Configuration Mode, reset the configuration register to the default of 0x01 to force the security appliance to read its startup configuration on boot: asa(config)#config-register 0x01
12. Use the following commands to view the configuration register setting: asa(config)#exit asa#show version
13. At bottom of the output of the show version command, you should see the following statement: Configuration register is 0x41 (will be 0x1 at next reload)
14. Save the current configuration with the copy run start command to make the above changes persistent: asa#copy run start Source filename [running-config]
15. Reload the security appliance: asa# reload System config has been modified. Save? [Y]es/[N]o:yes
Cryptochecksum: e5f81433 5493266b 4e24072 d71d5cbf
2157 bytes copied in 1.490 secs (2157 bytes/sec) Proceed with reload? [confirm]
When your security appliance reloads, you should be able to use your newly reset password to enter privileged mode.

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