Password Recovery Procedure for Cisco router 2600 and 2800 series

If you buy used Cisco device for your Cisco home lab, your used router/switch configuration most likely already erased to default configuration by the reseller. But what if you got a router/switch with password in it, or you forgot the password you gave to the device.


Cisco devices have a password recovery procedure that you can use to overcome this problem, some devices might have different procedure for password recovery.

The steps that I'm showing here is for Cisco 2600 and 2800 series routers, but most routers have the common steps to follow.
Some Cisco switches series have a button on the chassis that you must press for password recovery.
WARNING!!!
The password recovery procedure will wipe out all configuration in the router/switch, it is always a good idea to backup your configuration regularly and use the backup to reconfigure the router/switch after password recovery procedure.

To recover the password first you need to enter the ROMmon mode, for 2600 and 2800 series routers you need to change the configuration register from 0x2102 to 0x2142, then reset the router.
rommon 1 > confreg 0x2142
You must reset or power cycle for new config to take effect
rommon 2 > reset


Changing the configuration register from 0x2102 to 0x2142 tells the router to ignore the configuration in the NVRAM - where you place the password for the router.
This is why you must backup the configuration file to TFTP server regularly, so you can recover the configuration file if something like this happen in the future.
Your router will reload after the "reset" command in the ROMmon mode with no configuration, so it will ask again whether you want to enter the initial configuration prompt again, just answer no to this:
Would you like to enter the initial configuration dialog? [yes/no]: no

At this point you can enter the router without providing the password, if you check with show version command you will get that the configuration register has changed:

router# show version
Cisco Internetwork Operating System Software
IOS (tm) C2600 Software (C2600-I-M), Version 12.1(2)T, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2000 by cisco Systems, Inc.
Compiled Tue 16-May-00 15:15 by ccai
Image text-base: 0x80008088, data-base: 0x80865F64

ROM: System Bootstrap, Version 11.3(2)XA4, RELEASE SOFTWARE (fc1)

Router uptime is 3 minutes
System returned to ROM by reload
System image file is "flash:c2600-i-mz.121-2.T.bin"
cisco 2611 (MPC860) processor (revision 0x202) with 20480K/4096K bytes of memory.
Processor board ID JAB0317052N (1135645455)
M860 processor: part number 0, mask 49
Bridging software.
X.25 software, Version 3.0.0.
2 Ethernet/IEEE 802.3 interface(s)
1 Serial network interface(s)
32K bytes of non-volatile configuration memory.
8192K bytes of processor board System flash (Read/Write)  

Next thing is to fill in your new password or erase the password requirement from the router configuration mode. Use enable password or enable secret, saver to use enable secret.
router# configure terminal
router (config)# enable secret Cisco  

Don't forget to paste your backup configuration file to the terminal and save the running configuration:
router# write memory
or
router# copy running-config startup-config  


Last thing to do and the most important part is to change back the configuration register to 0x2102, or else everytime your router reloads it will ignore the configuration file.
router (config)# config-register 0x2142  


You can check with show version command that your configuration register value will change to 0x2102 after reloading the router.

router# show version
Cisco Internetwork Operating System Software
IOS (tm) C2600 Software (C2600-I-M), Version 12.1(2)T, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2000 by cisco Systems, Inc.
Compiled Tue 16-May-00 15:15 by ccai
Image text-base: 0x80008088, data-base: 0x80865F64

ROM: System Bootstrap, Version 11.3(2)XA4, RELEASE SOFTWARE (fc1)

Router uptime is 3 minutes
System returned to ROM by reload
System image file is "flash:c2600-i-mz.121-2.T.bin"
cisco 2611 (MPC860) processor (revision 0x202) with 20480K/4096K bytes of memory.
Processor board ID JAB0317052N (1135645455)
M860 processor: part number 0, mask 49
Bridging software.
X.25 software, Version 3.0.0.
2 Ethernet/IEEE 802.3 interface(s)
1 Serial network interface(s)
32K bytes of non-volatile configuration memory.
8192K bytes of processor board System flash (Read/Write)
 

Reload the router using reload command:
router# reload