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How to reset a cisco router password May 12, 2009

Posted by Ravindu Jayalath in Technical.
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Router>en

Password:

Password:

% Bad secrets

Check the config register value

Router>show version

………………………………………………………..

Cisco 1841 (revision 5.0) with 114688K/16384K bytes of memory.

Processor board ID FTX0947Z18E

M860 processor: part number 0, mask 49

2 FastEthernet/IEEE 802.3 interface(s)

191K bytes of NVRAM.

31360K bytes of ATA CompactFlash (Read/Write)

Configuration register is 0×2102

Then we need go to the Rom monitor mode. For that we can use several key sequences like Ctrl+BackSpace+Break while router is rebooted.

System Bootstrap, Version 12.3(8r)T8, RELEASE SOFTWARE (fc1)

Cisco 1841 (revision 5.0) with 114688K/16384K bytes of memory.

Self decompressing the image :

###############

monitor: command “boot” aborted due to user interrupt

We need to assign the config register value as 0×2142 where router will ignore the contents of NVRAM during the boot process.

rommon 1 > confreg 2142

rommon 2 > reset

Router>en

Router#show version

………………………………………………………..

Cisco 1841 (revision 5.0) with 114688K/16384K bytes of memory.

Processor board ID FTX0947Z18E

M860 processor: part number 0, mask 49

2 FastEthernet/IEEE 802.3 interface(s)

191K bytes of NVRAM.

31360K bytes of ATA CompactFlash (Read/Write)

Configuration register is 0×2142

Router(config)#enable secret 12345

Router(config)#config-register 2102

Router(config)#^Z

%SYS-5-CONFIG_I: Configured from console by console

Router#show version

………………………………………………………..

Cisco 1841 (revision 5.0) with 114688K/16384K bytes of memory.

Processor board ID FTX0947Z18E

M860 processor: part number 0, mask 49

2 FastEthernet/IEEE 802.3 interface(s)

191K bytes of NVRAM.

31360K bytes of ATA CompactFlash (Read/Write)

Configuration register is 0×2142 (will be 0×2102 at next reload)

Reboot the route after that.

………………………………………………………..

%LINK-5-CHANGED: Interface Vlan1, changed state to administratively down

Press RETURN to get started!

Router>en

Password:

Router#

We are good to go with new password.

Router#show version

………………………………………………………..

Cisco 1841 (revision 5.0) with 114688K/16384K bytes of memory.

Processor board ID FTX0947Z18E

M860 processor: part number 0, mask 49

2 FastEthernet/IEEE 802.3 interface(s)

191K bytes of NVRAM.

31360K bytes of ATA CompactFlash (Read/Write)

Configuration register is 0×2102

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Comments»

1. lamech - June 15, 2010

Thank you!
I tried to change the the password of a pre-configured cisco 1841 but it has failed to recorgnised both passwords!

2. justin - November 13, 2010

Thanks for the Info. Since cisco took this off their public site this has been very helpful.


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