If you are familiar with Cisco routers and then switches then you might have noticed that the Cisco ASA doesn’t offer the “erase startup-configuration” command. Of course we can erase our startup configuration but there are some other commands to achieve this.
This is the most simple option:
ciscoasa# write erase Erase configuration in flash memory? [confirm] [OK]
Just use “write erase” to remove the startup configuration and reboot your firewall. The other option is to use the factory default method:
ciscoasa(config)# configure factory-default 192.168.1.1 255.255.255.0 Based on the management IP address and mask, the DHCP address pool size is reduced to 253 from the platform limit 256 WARNING: The boot system configuration will be cleared. The first image found in disk0:/ will be used to boot the system on the next reload. Verify there is a valid image on disk0:/ or the system will not boot. Begin to apply factory-default configuration: Clear all configuration Executing command: interface management0/0 Executing command: nameif management INFO: Security level for "management" set to 0 by default. Executing command: ip address 192.168.1.1 255.255.255.0 Executing command: security-level 100 Executing command: no shutdown Executing command: exit Executing command: http server enable Executing command: http 192.168.1.0 255.255.255.0 management Executing command: dhcpd address 192.168.1.2-192.168.1.254 management Executing command: dhcpd enable management Executing command: logging asdm informational Factory-default configuration is completed
As you can see above this clears the configuration and enables the management interface with the IP address we specified. It also enables DHCP server and HTTP server so that we can connect through ASDM.