MicroNugget: How to Recover a Password on a Cisco Router

doing password recovery on a Cisco router happens all the time why because Cisco routers are awesome and they run for years and years without a hiccup but during those years and years spreadsheets are loss passwords our forgotten staff has changed and we get to a point where we have to do a configuration and nobody knows what the password is so first thing to do to do password recovery is configure an outage window because you have to reboot the router second go to where the router is you're gonna plug in with a console cable they look something like this you're gonna plug this end to the Cisco router into the console port this end into your laptop now hopefully your laptop has one of these serial ports actually hopefully it doesn't because you have a really old laptop if it does so you might need to get a USB to serial converter essentially it just looks like a USB port but has this on the end and you plug the serial port in there third you want to download a terminal program the one I'm gonna use here is teraterm but I'm dyslexia so so I only I write term first but you can also download one like putty or even you can use the archaic hyper term I don't know if hyper term can send a break character but it comes with old-school windows so feel free to use hyper term to do this plug into the console port turn the router off and back on now I've got a Cisco 2600 series router here so I just turned it on what you want to do is hit the break symbol you can do it any time you know from now until the the iOS has completely loaded iOS is the software of the device in the teraterm I need to go to the control and hit send brick now what it's gonna do is drop out to ramen ramen is not very friendly and think of it it's like the lost land of commands but it does support the question mark so I can type in the question mark the key that I'm looking for is this command called conf reg I type in comp reg and hit the enter key and it comes up and says hey here's your basic settings essentially the boot settings of the switch the one that we're after is this this configuration register does a lot of stuff one of the things is tells the router where to get its configuration from by this third digit being set to zero it says oh yeah look for your configuration in this area of memory called nvram that's non-volatile Ram we're gonna say actually I want to change that I want to get in there and say no I don't want to be in no no no yes you see this ignore system configuring info so it actually has a quick setting that we can go in there and say you know what I totally want to ignore my startup config now there's another way of doing this I'll show you in just a second you see what it did is change this configuration register from 0 X 20 102 to 0 X 21 42 that 4 says ignore your startup configuration completely I'm gonna hit no I don't want to change my configuration then all I need to do is reset the device now before I do that you can also type in if you're in a rush conf reg 0 X 21 42 and it does the same thing so if you know what you're after you don't have to go through that little wizard so I'm gonna type in the reset command which now reboots the router I'm gonna pause this let the router boot and show you what the results are the router now boots up to a screen that looks like this it thinks it has no configuration whatsoever because it really doesn't we told it to ignore the configuration by setting the configuration register to that now our goal was not to blow away the router configuration our goal is just to get past the passwords so here's what we do we go into the router and get into privilege mode now once I'm there I'm past all the passwords right privilege mode means I have full access to this now I want to restore the old config so I'm gonna type in copy startup config - running config that restores the old one with the passwords that I don't know but that's ok right because I'm already in privileged mode I'm already past all the passwords then you can see it restores and says oh this patent this routers hostname is now NAT now I can go in and do enable secret and change my password to whatever it is I want you know Cisco and ultra secure password and I'm good to go now I need to save my configuration by time it said and done but there is one thing that I want to make sure I don't forget to reset I'm gonna type in show version at the very bottom of this output it will tell me what the current configuration register is set to it's still set to 2142 instead of 2102 what does that mean the next time I reboot this device even if I save my configuration it's going to ignore the startup configuration again and boot as if it had none so I'm gonna go into global config mode before I do anything else and type config register 0x20 102 to revert it back to the old one now you'll see that when I do the show version command it's gonna say it's still 21 42 but the next reload will revert it to 21 Oh - that's great now I can save my configuration password has changed I am good to go oh one more item of note before I let you go when you do password recovery it will reboot with all the interfaces off so you want to go in after you do a password recovery situation and make sure you access each one of the interfaces and do a no shutdown that's because we've wiped out the configuration which had essentially all the no shutdown commands in there and that is one of the ones that is not restored when it comes back up so power on your interfaces save your config one more time now you're really good to go I hope this has been informative for you like to thank you for viewing

Channel: CBT Nuggets

Views: 28,712

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Id: pIYcHvOMAmc

Length: 5min 19sec (319 seconds)

Published: Tue Feb 05 2013