Hard Reset Cisco Switch – C3850
Background
The switch was in stack and it was dismantled. I was about to erase the config. However, no exec was configured under line con 0. I was not able to do anything with console access.
Solution
Switch to Rommon mode
Similar to router system, we can break the system bootup to rommon mode. In the switch, it displays as switch instead of rommon. This is done by pressing the MODE button for at least 15 seconds.
- Enter
flash_init. Then we can show the files in the flash:.
2. Enter SWITCH_IGNORE_STARTUP_CFG=1 and then boot . System will load without loading start-up config.
Erase the config
However, by write erase it would not delete all the config. We can delete the nvram config by delete flash:nvram_config. If there is a backup file, delete that too by delete flash:nvram_config_bkup. Then reload the system. It will reset to factory default.
Comments
After I manipulated the confreg parameter and reloaded the switch, there were 2 more files called startup-config-pre.txt and running-config-pre.txt. I deleted these 2 files. But it didn’t affect the system config.
If the switch is in stack, we follow the process here for the whole stack. The switches will sync the config file from the active switch.
Next time, I can try to delete the nvram_config in the rommon mode.