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
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.