The startup configuration can be bypassed by booting into ROMMON or during normal operation. In either case, a reboot is required.

This is particularly useful, for example, if you need to perform a password recovery because you have forgotten your password, or for troubleshooting purposes.

Configuration in IOS# 

Switch# configure terminal
! to activate
Switch(config)# system ignore startup-config

! to deactivate
Switch(config)# no system ignore startup-config

Configuration in ROMMON#

In the background, the IOS command simply sets the ROMMON variable SWITCH_IGNORE_STARTUP_CONFIG to 1 or 0 which we can also do manually.

In ROMMON mode, you set the variable as follows in order to bypass the startup configuration:

set SWITCH_IGNORE_STARTUP_CONFIG=1

The sh romvar command displays the current ROMMON variables.