Brent Saltzman


Interested in all things technology with a passion for analog, design, audio, and anything that sparks creativity and imagination.


Factory Reset a Cisco Catalyst 3750 Series Switch

If you're wanting a reliable backbone to your home network an obvious choice is a used enterprise level Cisco Catalyst 3750 series switch. These can be found on eBay anywhere from ~$50-$100 which is dirt cheap compared to consumer options and nowhere near as reliable.

c3750x

If you need to reset a Cisco 3750 or other Catalyst series switches back to a factory default configuration or if you've forgotten your admin password, here's what you can do to reset it. You'll need a serial console cable and a Serial to USB Adapter if your computer doesn't have a serial port. I've found the Prolific Chipset adapters to work the best.

Connect to the serial port of your switch and open up a console session in a terminal emulator such as Putty.

Power off your switch if it's already booted up. Once you have it powered off, hold down the Mode button and apply power until you see a prompt like below

Switch:  

Now type flash_init and press enter. Your console should show something like the following:

switch: flash_init  
Initializing Flash…  
flashfs[0]: 547 files, 19 directories  
flashfs[0]: 0 orphaned files, 0 orphaned directories  
flashfs[0]: Total bytes: 32514048  
flashfs[0]: Bytes used: 15487488  
flashfs[0]: Bytes available: 17026560  
flashfs[0]: flashfs fsck took 11 seconds.  
…done Initializing Flash.

Let's take a look at the flash storage. We're looking for config.text and vlan.dat. Type dir flash: and press enter.

switch: dir flash:  
Directory of flash:/

2  -rwx  564       <date>               vlan.dat  
3  -rwx  1914      <date>               private-config.text  
5  drwx  192       <date>               c3750-ipbasek9-tar.122-55.SE1  
6  -rwx  3096      <date>               multiple-fs  
7  -rwx  2289      <date>               config.text  

Hint: if you want to make a backup copy of the old config, you can by typing:

switch: rename flash:config.text flash:config.text.old  

Let's delete the config.text and vlan.dat files to reset the configuration for this switch. Type del flash:config.text and del flash:vlan.dat. Confirm Y on both.

switch: del flash:config.text  
Are you sure you want to delete “flash:config.text” (y/n)? Y  
File “flash:config.text” deleted

switch: del flash:vlan.dat  
Are you sure you want to delete “flash:vlan.dat” (y/n)? Y  
File “flash:vlan.dat” deleted  

at the prompt type boot to reboot the switch and go through the initial configuration process.

switch: boot  

That's all there is to it! You should now be back at a switch with a default factory configuration with the password of cisco. You can proceed to configure your switch.

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