Cisco Catalyst 3850 Factory Reset¶
Complete procedure for factory resetting Cisco Catalyst 3850 series switches, including password recovery and IOS image reinstallation.
Prerequisites¶
| Item | Details |
|---|---|
| Console Cable | RJ-45 to USB/Serial console cable |
| Terminal Software | PuTTY, TeraTerm, or similar (9600 baud, 8-N-1) |
| USB Drive | FAT32 formatted with IOS .bin file (if reinstalling) |
| Physical Access | Access to Mode button on switch front panel |
Method 1: Software Factory Reset (With Access)¶
Use this method if you have enable access to the switch.
Steps¶
! Enter privileged exec mode
Switch> enable
Switch#
! Factory reset all settings and data
Switch# factory-reset all
! For secure erasure (overwrites data)
Switch# factory-reset all secure
Data Loss
Factory reset erases ALL configuration, certificates, and user data. Back up your configuration first using copy running-config tftp: or copy running-config usbflash0:
Method 2: Mode Button Reset (No Password Required)¶
Use this method when you don't have the enable password.
Part 1: Enter ROMMON Mode¶
- Power off the switch
- Locate the Mode button on the front panel
- Press and hold the Mode button
- While holding Mode, power on the switch
- Continue holding until:
- LEDs blink after ~3 seconds
- LEDs stop blinking after ~10 seconds
- SYST LED turns solid green
- Release the Mode button
- Switch enters ROMMON mode (
switch:prompt)
Part 2: Boot from USB and Reset¶
| Step | Command | Description |
|---|---|---|
| 1 | flash_init |
Initialize flash filesystem |
| 2 | dir usbflash0: |
List USB drive contents |
| 3 | set BOOT usbflash0:<filename>.bin |
Set boot image from USB |
| 4 | boot |
Boot the system |
Boot Variable
The set BOOT command sets the boot image for this session only. Use boot system in config mode to make it permanent.
Part 3: Factory Reset and Configure Boot¶
Once booted:
! Answer "no" to config dialogue
! Answer "yes" to terminate autoinstall
! Enter privileged mode
Switch> enable
! Perform factory reset (confirm twice)
Switch# factory-reset all
! Wait for reboot to complete...
! After reboot, enter privileged mode again
Switch> enable
! Format flash to remove old files
Switch# format flash:
! Confirm twice when prompted
! Copy IOS image to flash
Switch# copy usbflash0:<filename>.bin flash:
! Press Enter to accept default destination filename
! Verify copy was successful
Switch# dir flash:
! Enter configuration mode
Switch# configure terminal
! Set permanent boot image
Switch(config)# boot system flash:<filename>.bin
! Exit config mode
Switch(config)# exit
! Save configuration
Switch# write memory
! Reload to verify
Switch# reload
Method 3: Password Recovery Only¶
Use this method to reset the password without losing configuration.
Steps¶
-
Enter ROMMON mode (see Method 2, Part 1)
-
Set switch to ignore startup config:
switch: SWITCH_IGNORE_STARTUP_CFG=1 switch: boot -
After boot, reset the password:
Switch> enable Switch# configure terminal Switch(config)# enable secret <new-password> Switch(config)# exit Switch# write memory -
Re-enable startup config:
Switch# configure terminal Switch(config)# no system ignore startupconfig switch all Switch(config)# exit Switch# write memory Switch# reload
LED Indicators¶
| LED | State | Meaning |
|---|---|---|
| SYST | Off | System not powered |
| SYST | Green | System operational |
| SYST | Amber | System error/POST failure |
| SYST | Blinking Green | Booting/Mode button held |
Common Commands Reference¶
| Command | Purpose |
|---|---|
show version |
Display IOS version and hardware info |
show boot |
Display boot configuration |
dir flash: |
List flash contents |
dir usbflash0: |
List USB drive contents |
erase startup-config |
Erase startup configuration only |
factory-reset all |
Complete factory reset |
factory-reset all secure |
Secure erase (DoD standard) |
Troubleshooting¶
Switch Won't Enter ROMMON Mode¶
- Ensure Mode button is held before powering on
- Hold for at least 10 seconds until LEDs stop blinking
- Try a different console cable/terminal settings
USB Drive Not Detected¶
- Ensure FAT32 format (not NTFS or exFAT)
- Try a different USB port (front vs rear)
- Verify .bin filename has no spaces or special characters
Boot Fails After Reset¶
- Verify IOS image copied correctly:
dir flash: - Check boot variable:
show boot - Re-copy image if MD5 checksum fails
Stack Member Issues¶
For stacked switches, perform factory reset on each member:
Switch# factory-reset switch <switch-number>