(ROM Monitor) is the bootstrap firmware embedded on the motherboard of Cisco routers and switches. When you power on an ASR1000, the CPU has no memory, no routing protocols, and no interfaces active. The first code to execute resides in a small ROM chip. That code is ROMMON.
The 17.3(1r) release is a major milestone for the ASR 1000 series, often required for compatibility with modern Cisco IOS XE 17.x software branches A critical characteristic of this version is its irreversibility asr1000-rommon.173-1r.spa.pkg
: Once upgraded to version 17.3(1r) on supported platforms, you cannot revert or downgrade to a ROMMON version earlier than 17.3(1r). ⚙️ How to Upgrade ROMMON (ROM Monitor) is the bootstrap firmware embedded on
If your compliance requires NIST SP 800-124 (firmware integrity), 173-1r meets the baseline. That code is ROMMON
Without this upgrade, you may see the following failure when booting a new IOS-XE: