How to Reset Cisco Router Password

In this post I will show you how to reset the password on a Cisco router. I will be using a Cisco 1841 router to demonstrate this process.

STEP 1: Connect the power to the Cisco 1841 router

STEP 2: Connect the console cable to the console port of the router.

I have a USB to Serial cable and on my computer, this shows as Com 3.

STEP 3: Use either Putty, Teraterm or HyperTerminal to connect the router’s.

In my case, I notice that the serial connected is at COM 3 . I use HyperTerminal for this demonstration.

For some reason, I could not get the break key sequence to work (I tried Ctrl+Break, Break, Alt+], etc…), I had to simulate the break key sequence this way:

STEP 4: HyperTermonal Setup

Use HyperTerminal, connect to the router using 1200 Baud rate, no parity, 8 data bits, 1 stop bit, no flow control.

Then press the space bar for 15 seconds, I saw garbage characters.

STEP 5: Then disconnect the HyperTerminal and reconnect using the default parameter of 9600 Baud rate.

Now I was in Rommon mode.

STEP 6: In Rommon, I perform this:

rommon 1 > confreg 0x2142

You must reset or power cycle for new config to take effect

rommon 2 > i (to restart)
Router>enable
Router#config t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#enable secret mysecret
Router(config)#config-register 0x2102
Router(config)#exit
Router#wr
Building configuration…
[OK]
Router#reload
Proceed with reload? [confirm]

After the router restarted, I could log into the manager mode with the new password “mysecret”

Router>
Router>enable
Password:
Router#

Now I can show the running configuration of the router as follows:

Router#show run
Building configuration…
Current configuration : 716 bytes
!
version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname Router
!
boot-start-marker
boot-end-marker
!
enable secret 5 $1$pxZH$ymjW3jxDFjp6lN.A0f.Zo1
!
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
no aaa new-model
ip subnet-zero
ip cef
!
!
no ftp-server write-enable
!
interface FastEthernet0/0
no ip address
shutdown
duplex auto
speed auto
!
interface FastEthernet0/1
no ip address
shutdown
duplex auto
speed auto
!
ip classless
!
!
no ip http server
no ip http secure-server
!
!
control-plane
!
!
line con 0
line aux 0
line vty 0 4
login
!
end
Router#


As you can see that I am able to access my Cisco router after clearing the existing unknown password. This tip is very helpful when you buy reconditioned hardware. The total time of this lab was 10 minutes.