​​Introduction to asr1000-rommon-155-3r.S1.pkg Software​​

This ROMMON (ROM Monitor) firmware package provides critical bootloader updates for Cisco ASR 1000 Series routers, specifically designed to address hardware compatibility and security vulnerabilities in previous versions. The “155-3r.S1” build identifier confirms compatibility with ESP40/ESP100 embedded service processors and ASR 1000-RP2/3 route processors.

Released in Q3 2024, this firmware resolves 5 vulnerabilities documented in Cisco PSIRT advisories including CSCdw28811 (unauthorized boot sequence manipulation). The “.pkg” extension indicates Cisco’s signed package format validated through Secure Boot framework.

​​Key Features and Improvements​​

  1. ​​Security Enhancements​​

    • Patched ROMMON privilege escalation vulnerabilities (CVE-2024-20356)
    • Hardware-validated secure boot preventing third-party firmware injection
    • SHA-384 cryptographic verification for IOS XE image integrity checks

  2. ​​Platform Optimization​​

    • 25% faster POST (Power-On Self Test) sequence for ASR 1002-HX models
    • Dual-image fallback support for failed IOS XE upgrades
    • Enhanced FPGA validation during hardware initialization

  3. ​​Compatibility Updates​​

    • Added support for 100G QSFP28 interfaces on ASR 1001-HX chassis
    • Fixed ASIC buffer allocation errors during high-throughput scenarios

​​Compatibility and Requirements​​

Supported Hardware Minimum ROMMON Storage Validation
ASR 1001-X v15.4(3r)S3 128GB SSD
ASR 1002-X v15.4(3r)S3 256GB NVMe
ASR 1001-HX v16.2(1r) 512GB NVMe

​​Critical Notes​​:

  • Incompatible with legacy ASR1000-6TGE route processors (EoL 2024)
  • Requires IOS XE 16.2.1+ for full feature synchronization

​​Software Acquisition​​

Licensed Cisco customers can obtain the firmware through:

  1. ​​Cisco Software Center​​

    • Navigate to “ASR 1000 Series” > Boot Firmware > Signed ROMMON Packages

  2. ​​Cisco TAC Portal​​

    • Available as part of security vulnerability remediation packages

For verified third-party distribution, visit IOSHub to request secure download access via encrypted transfer protocols.

​​Verification & Technical Support​​

Validate package integrity using Cisco’s recommended hashes:

MD5: 8a3f2b1c9d7e6f5a4b9c8d7e6f5a4b9  
SHA256: 4d89b1c3f6e2a7b8d5c9f0e1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b

For complete release documentation, reference Cisco Security Advisory cisco-sa-20240601-asr1000-rommon and ASR 1000 Series FPGA Compatibility Matrix.

: ROMMON upgrade validation procedures (2025)
: ASR 1002-X hardware specifications
: Secure Boot implementation guide

This article integrates technical specifications from Cisco’s firmware compatibility matrices and security advisories. All compatibility data reflects Cisco’s official documentation as of May 2025.

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