This document describes how to modify certain system parameters using CLI commands on Catalyst 9000 switches running Cisco® IOS-XE. These commands are an alternative to changing the configuration-register value on Cisco® IOS.
Config-register is a 16-bit software register value that is preconfigured in NVRAM and can be used to change switch behavior in several ways, such as:
how the switch boots (into ROMmon, NetBoot)
options while booting (ignore configuration, disable boot messages)
console speed (baud rate for a terminal emulation session)
On Classic platforms that run on Cisco IOS software, the configuration register can be set from configuration mode using the config-register command or from ROMmon using the confreg command. Theshow versioncommand allows viewing the current setting of the configuration register.
On Catalyst 9000 switches that run on Cisco IOS-XE, the config-register command was still available to configure, and the current setting as appearing in show version as well, but the actual config-register command was ineffective and was malfunctioning causing confusion.
This is because Cisco IOS-XE doesn’t use this config-register command and provides alternate CLI commands to handle the same.
Note: The incorrect display of configuration register value on show version output is removed from 16.12.4 and 17.3.1 release onwards.
Here are the equivalent CLI commands on Cisco IOS-XE that allows user to perform same tasks done by setting config-register value on Cisco IOS.
Note: If a system running on Cisco IOS-XE fails to boot for 5 consecutive times in less than 25mins of uptime for each reload, then the software auto-sets ROMmon variable MANUAL_BOOT="yes". In other words, if a system fails to boot for any reason it auto boots into ROMmon after 5 consecutive tries.
If both ignore config and disable password recovery is enabled then the respective ROMmon variables are set.
If both these variables are set, the switch prompts during bootup to confirm before erasing the startup-config.
Both ignore startup configuration and disable password are set This will result in erasing the startup config Do you want to Erase the config? Default: n, Answer y/n: User response is YES, erasing the startup config Removing FIPS Key. Disabling FIPS MODE All TCP AO KDF Tests Pass