Do a Clean OS Install on ASA 5506-X firewall

This Document is © by Microsolutions Information Systems (PVT) Ltd. 


Cisco ASA with or without OS installed.

Console Connectivity to device

Correct ASA OS to selected hardware model (Eg. asa941-lfbff-k8.SPA) downloaded from cisco web site

Correct ASDM maching to selected ASA software

TFTP server which connected to same network

Steps of formatting:

  1. Connect to the console connectivity connected to asa 5500-x device
  2. Reload the device and go to ROMMON Mode using break sequence.

Use BREAK or ESC to interrupt boot.

  1. Use ROMMON Mode with below commands to upload ASA OS

rommon 1 > erase disk0:                    – will take 5-10 minutes

rommon 1 > ADDRESS=             – address for ASA device

rommon 2 > NETMASK=

rommon 3 > SERVER=              – address of TFTP server

rommon 4 > IMAGE=asa941-lfbff-k8.SPA        – OS file Name

rommon 5 > sync

rommon 6 > tftpdnld





               IMAGE: asa941-lfbff-k8.SPA

             MACADDR: 18:8b:9d:40:51:6e

           VERBOSITY: Progress

               RETRY: 40

          PKTTIMEOUT: 7200

             BLKSIZE: 512

            CHECKSUM: Yes

                PORT: GbE/1

             PHYMODE: Auto Detect

Receiving asa941-lfbff-k8.SPA from!!!!!!!!!!!!!!!!!!!!

File reception completed.

Boot buffer bigbuf=348bd018

Boot image size = 69454656 (0x423cb40) bytes

[image size]      69454656

[MD5 signaure]    449c9c79c65dfc756b843a1285267d53

LFBFF signature verified.

INIT: version 2.88 booting

Starting udev

Configuring network interfaces… done.

Populating dev cache

dosfsck 2.11, 12 Mar 2005, FAT32, LFN

Logical sector size is zero.

dosfsck(/dev/sdb1) returned 1

mount: wrong fs type, bad option, bad superblock on /dev/sdb1,

       missing codepage or helper program, or other error

       In some cases useful info is found in syslog – try

       dmesg | tail or so.

mount: /dev/sdb1 is write-protected, mounting read-only

mount: wrong fs type, bad option, bad superblock on /dev/sdb1,

       missing codepage or helper program, or other error

       In some cases useful info is found in syslog – try

       dmesg | tail or so.

Processor memory 1242769653

Compiled on Sat 21-Mar-15 11:42 PDT by builders

Total NICs found: 13

i354 rev03 Gigabit Ethernet @ irq255 dev 20 index 08 MAC: 188b.9d40.516e

ivshmem rev03 Backplane Data Interface     @ index 09 MAC: 0000.0001.0002

en_vtun rev00 Backplane Control Interface  @ index 10 MAC: 0000.0001.0001

en_vtun rev00 Backplane Int-Mgmt Interface     @ index 11 MAC: 0000.0001.0003

en_vtun rev00 Backplane Ext-Mgmt Interface     @ index 12 MAC: 0000.0000.0000


INFO: Unable to read firewall mode from flash

       Writing default firewall mode (single) to flash

Verify the activation-key, it might take a while…

Failed to retrieve permanent activation key.

Running Permanent Activation Key: 0x00000000 0x00000000 0x00000000 0x00000000 0x00000000

The Running Activation Key is not valid, using default settings:


Licensed features for this platform:

Maximum Physical Interfaces       : Unlimited      perpetual

Maximum VLANs                     : 5              perpetual

Inside Hosts                      : Unlimited      perpetual

Failover                          : Disabled       perpetual

Encryption-DES                    : Enabled        perpetual

Encryption-3DES-AES               : Disabled       perpetual

GTP/GPRS                          : Disabled       perpetual

AnyConnect Premium Peers          : 2              perpetual

AnyConnect Essentials             : Disabled       perpetual

Other VPN Peers                   : 10             perpetual

Total VPN Peers                   : 12             perpetual

Shared License                    : Disabled       perpetual

AnyConnect for Mobile             : Disabled       perpetual

AnyConnect for Cisco VPN Phone    : Disabled       perpetual

Advanced Endpoint Assessment      : Disabled       perpetual

Total UC Proxy Sessions           : 2              perpetual

Botnet Traffic Filter             : Disabled       perpetual

Cluster                           : Disabled       perpetual


This platform has a Base license.

INFO: Unable to read cluster interface-mode from flash

        Writing default mode “None” to flash

Encryption hardware device: Cisco ASA Crypto on-board accelerator (revision 0x1)

Cisco Adaptive Security Appliance Software Version 9.4(1)


                                Output Omitted!


                                INFO: Starting SW-DRBG health test…

INFO: SW-DRBG health test passed.

Pre-configure Firewall now through interactive prompts [yes]?      – press Enter

Firewall Mode [Routed]:                                         – press enter

Enable password [<use current password>]:                        – press enter

Allow password recovery [yes]?                                  – press enter

Clock (UTC):                                                   – set date

  Year [2017]:

  Month [Mar]:

  Day [17]:

  Time [06:11:12]:

Management IP address:               

Management network mask:

Host name: asa

Domain name:

IP address of host running Device Manager:                       – press enter


  1. After configurations asa will prompt to asa exe mode
  2. Format the flash using below command: this will take 10-20 minutes

asa# erase flash:


  1. Copy OS file to flash

asa# copy tftp: flash:

Address or name of remote host []?

Source filename []? asa941-lfbff-k8.SPA

Destination filename [asa941-lfbff-k8.SPA]?

Accessing tftp://…!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


Computed Hash   SHA2: ca4413c9743cd0e59444215b771e836e





Embedded Hash   SHA2: ca4413c9743cd0e59444215b771e836e





Digital signature successfully validated

Writing file disk0:/asa941-lfbff-k8.SPA…


69454656 bytes copied in 151.520 secs (459964 bytes/sec)


  1. Verify file with ‘asa# show flash:’ command

asa# sh flash:

–#–  –length–  —–date/time——  path

   10  69454656    Mar 17 2017 06:40:31  asa941-lfbff-k8.SPA


  1. Configure Boot path

asa(config)# boot system flash:/asa941-lfbff-k8.SPA

INFO: Converting flash:/asa941-lfbff-k8.SPA to disk0:/asa941-lfbff-k8.SPA


  1. Enable core dump

asa(config)# coredump enable


  1. Save Configurations

asa(config)# copy running-config startup-config


  1. Check Boot image is configured correctely

asa# sh bootvar

BOOT variable = disk0:/asa941-lfbff-k8.SPA

Current BOOT variable = disk0:/asa941-lfbff-k8.SPA

CONFIG_FILE variable =

Current CONFIG_FILE variable =


  1. Reload device

asa# reload

Proceed with reload? [confirm]




Shutting down isakmp

Shutting down sw-module

Shutting down License Controller

Shutting down File system



Process shutdown finished


Rom image verified correctly

Cisco Systems ROMMON, Version 1.1.8, RELEASE SOFTWARE

Copyright (c) 1994-2015  by Cisco Systems, Inc.

Compiled Thu 06/18/2015 12:15:56.43 by builders

Current image running: Boot ROM1

Last reset cause: PowerCycleRequest

DIMM Slot 0 : Present

Platform ASA5506 with 4096 Mbytes of main memory

MAC Address: 18:8b:9d:40:51:6e


Use BREAK or ESC to interrupt boot.

Use SPACE to begin boot immediately.


Located ‘.boot_string’ @ cluster 16989.


Attempt autoboot: “boot disk0:/asa941-lfbff-k8.SPA”

Located ‘asa941-lfbff-k8.SPA’ @ cluster 10.



Output Omitted!



  1. Set ip addresses and login settings

asa(config)# conf t

asa(config-if)# int m 1/1

asa(config-if)# no ip address

asa(config-if)# int gi 1/1

asa(config-if)# ip address      -applying ip address to inside network interface

asa(config-if)# no shut

asa(config-if)# nameif inside

asa(config)# http server enable                           – enabling http server for asdm connectivity

asa(config)# http inside        

asa(config)# username cisco password cisco privilege 15

asa(config)# aaa authentication http console LOCAL

asa(config)# aaa authentication ssh console LOCAL

asa(config)# aaa authentication enable console LOCAL


  1. Copy ASDM image to ASA

asa(config)# copy tftp: flash:

Address or name of remote host []?

Source filename [asdm-761.bin]?

Destination filename [asdm-761.bin]?

Accessing tftp://…!!!!!!!!!!!!!

Writing current ASDM file disk0:/asdm-761.bin


asa(config)# asdm image flash:/asdm-761.bin         -setting asdm for asa


  1. Activate ASA licenses with activation key

asa(config)# activation-key XXXXXXX XXXXXXX XXXXXX XXXXXX XXXXXX

Validating activation key. This may take a few minutes…

Failed to retrieve permanent activation key.

Failover is different.

   running permanent activation key: Restricted(R)

   new permanent activation key: Unrestricted(UR)

WARNING: The running activation key was not updated with the requested key.

Proceed with update flash activation key? [confirm]

The flash permanent activation key was updated with the requested key,

and will become active after the next reload.


16. Now ASA device can reimage with firepower​ service software. check this post to find reimage process