Information About ROM Monitor Firmware
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 ASR 9000 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.
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.
ROMMON A and ROMMON B
Each node in a Cisco ASR 9000 Series Router includes two copies of ROM Monitor: ROMMON A and ROMMON B. During power on, ROMMON A loads first. If ROMMON A detects the presence of ROMMON B, it checks the compatibility and integrity of the ROMMON B code. If ROMMON B passes these tests, ROMMON A passes control of the router to ROMMON B.
Normally, you only upgrade ROMMON B. ROMMON A is a backup for ROMMON B. When you upgrade the ROMMON B, the router uses the unmodified ROMMON A if the ROM Monitor upgrade is interrupted or fails for any reason.
Failures are most likely to occur during ROMMON upgrades or downgrades and unlikely to fail during normal usage. A failure in ROMMON A results in an inactive card that must be returned to the authorized merchandiser.
We recommend that you upgrade ROMMON on all the boards to the latest version provided in FPD pie for any particular release.
Upgrading or Downgrading a Single Node or All Nodes
The upgrade and downgrade procedures for ROMMON firmware are the same. Install a higher version to upgrade the firmware, or a lower version to downgrade the firmware.
ROM Monitor operates on every node within the router. During an upgrade or downgrade, the ROMMON firmware is copied into hardware EEPROMs in the router.
For most upgrades, we recommend upgrading or downgrading the ROMMON firmware on all nodes. You can also upgrade or downgrade a single node, which is useful when moving a card between two routers or adding a card that is not running the correct ROM Monitor version. When you upgrade a single node that uses ROM Monitor in both the CPU0 and SP modules, such as a line card node, we recommend that you upgrade both modules to the same ROM Monitor version.
Reloading Nodes After a ROMMON Firmware Change
The new ROMMON firmware is not active on a node until the card is reloaded. For example, if you upgrade a single node, you must reload that node only after the upgrade. If you upgrade or downgrade all nodes, you must also reload all nodes to activate the new ROMMON version.
To gracefully reload all nodes, reload the standby RSP, perform a redundancy switchover, reload the second RSP, and then reload all other nodes in the system.
If the router does not contain a redundant standby RSP, or if you wish to perform a cold restart, you can also reload all nodes at the same time, including the primary RSP. Remember that a cold restart results in router downtime while the cards reboot.