Cisco ISR900
Start the console session.
Plug in serial cable to device from PC COM1 port
Open PuTTY and select "Serial" connection type, leave baud rate (Speed) and other settings as default.
Plug power into device and if a power button exists, turn it on.
Access the Rommon prompt.
Repeatedly press Ctrl C keys. Example output:
System Bootstrap, Version 15.8(3r)M0b, RELEASE SOFTWARE (fc1) Copyright (c) 2018 by cisco Systems, Inc. Compiled Mon 03-Sep-2018 9:01:14.57 C921-4PLTEAU platform with 1048576 Kbytes of main memory System Integrity Status: 0x00000000 Current image running: Upgrade Last reset cause: Power On Rom image verified correctly . rommon 1 >
Bypass any configured login.
Type the confreg command followed by a string value instruction to ignore the current configuration when booting up:
rommon 1 > confreg 0x2142 You must reset or power cycle for new config to take effect
Type the reset command:
rommon 2 > reset System will now reset and boot from Upgrade ROMMON Please wait while the system restarts. System Bootstrap, Version 15.8(3r)M0b, RELEASE SOFTWARE (fc1)
The boot process should bring you to an initial configuration dialog prompt. Type n then the Enter key, and Enter again when prompted to get started:
--- System Configuration Dialog --- Would you like to enter the initial configuration dialog? [yes/no]: n Press RETURN to get started!
Erase any log files, vlan data and all configuration settings.
Type the enable command to enter privileged command mode, then the dir command, then the del command pattern matching where necessary to erase non-OS image files:
Router>enable Router#dir Directory of flash:/ 1 -rw- 304 Sep 17 2020 10:04:38 +00:00 fwlogfile 2 -rw- 34 Oct 8 2019 23:53:40 +00:00 pnp-tech-time 3 -rw- 56723 Oct 8 2019 23:53:52 +00:00 pnp-tech-discovery-summary 4 drw- 0 Jul 15 2020 07:26:46 +00:00 Logs 15 -rw- 65461428 Jul 15 2020 07:38:48 +00:00 c900-universalk9-mz.SPA.159-3.M0a.bin 1942310912 bytes total (1875034112 bytes free) Router#del Logs/* Delete filename [/Logs/*]? Delete flash:/Logs/log_20200715-172648? [confirm]y Delete flash:/Logs/log_20200715-200456? [confirm]y Delete flash:/Logs/log_20200804-104926? [confirm]y Delete flash:/Logs/log_20200806-095357? [confirm]y Delete flash:/Logs/log_20200821-124454? [confirm]y Delete flash:/Logs/log_20200821-124455? [confirm]y Delete flash:/Logs/log_20201022-152340? [confirm]y Delete flash:/Logs/log_20201101-081150? [confirm]y Delete flash:/Logs/log_20201129-024442? [confirm]y Delete flash:/Logs/log_20201210-120005? [confirm]y Router#rmdir Logs Remove directory filename [Logs]? Delete flash:/Logs? [confirm]y Removed dir flash:/Logs Router#del fwlog* Delete filename [fwlog*]? Delete flash:/fwlogfile? [confirm]y Router#del pnp* Delete filename [pnp*]? Delete flash:/pnp-tech-time? [confirm]y Delete flash:/pnp-tech-discovery-summary? [confirm]y
Type the erase startup-config command, and confirm with y:
Router#erase startup-config Erasing the nvram filesystem will remove all configuration files! Continue? [confirm]y[OK] Erase of nvram: complete
TIP: You can verify vlan data and configuration is gone with the show vlans and show startup-config commands respectively:
Router#show vlans No Virtual LANs configured. Router#show startup-config startup-config is not present
Reboot the device and set it back to normal mode.
Type the reload command and confirm with y:
Router#reload Proceed with reload? [confirm]y *Mar 1 00:30:54.279: %SYS-5-RELOAD: Reload requested by console. Reload Reason: Reload Command.
Interrupt the boot process again as done in step 2, then at the rommon prompt type the confreg command followed by a different string value instruction to no longer ignore the configuration:
rommon 1 > confreg 0x2102 You must reset or power cycle for new config to take effect
Lastly type the reset command:
rommon 2 > reset
Copy all the output from the session into your records.
Right-click PuTTY's titlebar, from that dropdown menu click on "Copy All to Clipboard"
Open the file of record certifying the deconfiguration of this device and use CTRL V to paste all the output from PuTTY into that file. Formatting the text with a fixed-width font helps it look more readable.
End the session.
Turn off/unplug the device and close PuTTy.