The ROM Monitor, which is also known as ROMMON, is a bootstrap program that initializes the hardware and boots the Cisco IOS XR firmware when you power on or restart a Cisco XR 12000 Series Router. ROM Monitor upgrades can be required to resolve firmware defects or support new features. Typically, ROM Monitor upgrades are infrequent and not required for every Cisco IOS XR software upgrade.
The ROM Monitor firmware on all Route Processors (RP)s must be compatible with the current Cisco IOS XR software release running on the router before it is upgraded to the latest Cisco IOS XR Software Release. For minimum ROM Monitor requirements, see Software/Firmware Compatibility Matrix at the following URL:
If the router is brought up with an incompatible version of the ROM Monitor software, then the standby RP may fail to boot.
ROMMON versions are backward compatible. You need not downgrade the ROMMON versions if the current version is higher than the listed compatible version.
The upgrade and downgrade procedures for ROM Monitor are the same. During the upgrade or downgrade process, you select the firmware that is used for ROM Monitor. This firmware can represent an upgrade or a downgrade. The firmware must be compatible with the hardware, but it need not be a later version of the ROM Monitor already installed. During an upgrade or downgrade, the firmware is copied into hardware EEPROMs in the router.
Boothelper software is an additional software that extends the capabilities of ROM Monitor on a Cisco XR 12000 Series Router. Without the Boothelper, ROM Monitor can load images from disk0, disk1, and bootflash. With Boothelper, ROM Monitor can load images from disk0, disk1, bootflash, compact flash, and TFTP servers.
The Boothelper software is also stored in bootflash and can be upgraded or downgraded by replacing the software in the bootflash with a different Boothelper image.