Firepower 4100 Chassis DIMM Memory Failure, Security Module Inoperable

Issue

A Cisco Firepower 4115 chassis experienced an unexpected reboot and failed to return to operational status. These symptoms were observed:

• FMC UI shows the FTD status as "Disabled."

• The Chassis Manager UI shows the logical instance with Status: Security module fault.

  

• The Chassis Manager UI displays the security engine as Degraded.

  

• Multiple related faults for DDR4/DIMM memory, security module, and storage appear in the FXOS CLI.

  fxos# show fault
  Severity  Code     Last Transition Time     ID       Description
  --------- -------- ------------------------ -------- -----------
  Critical  F1236    2026-06-26T05:50:35.387   2443029 Health LED of server 1/1 shows error. Reason: DDR4_P1_A1_ECC:Sensor Threshold Crossed;
  Major     F1546    2026-06-26T22:11:30.870   2443026 Security Module 1 is in failed state. Error: Security module is downgraded (or) not acknowledged. Reason: DIMM or CPU degraded
  Major     F0317    2026-06-26T22:05:08.375   2443211 Server 1/1 (service profile: org-root/ls-ssp-sprof-1) health: inoperable
  Major     F1761    2026-06-26T05:52:40.467   2443450 Physical memory size 180224 on server 1/1 is smaller than expected.
  Major     F0185    2026-06-26T05:31:08.858   2442844 DIMM DIMM_A1 on server 1/1 operability: inoperable
  Info      F0461    2025-08-26T04:24:40.271   1895361 Log capacity on Management Controller on server 1/1 is very-low

• The Chassis server and memory status details show inoperable DIMM component.

  fxos# show server status detail
  Server 1/1:
      Slot Status: Equipped
      Equipped Conn Path: A
      Equipped Conn Status: A
      Equipped Managing Instance: A
      Availability: Unavailable
      Admin State: In Service
      Overall Status: Degraded
      Oper Qualifier: Memory Inoperable
      Discovery: Complete
      Current Task:
      Check Point: Discovered
  
  fxos# show server memory detail
  Server 1/1:
      Array 1:
          CPU ID: 1
          Current Capacity (MB): 180224
          Error Correction: Undisc
          Max Capacity (MB): 9437184
          Max Devices: 24
          Populated: 12
          DIMMS:
          ID 1:
              Location: DIMM_A1
              Presence: Equipped
              Overall Status: Inoperable
              Visibility: No
              Vendor: NO DIMM
              Vendor Part Number: NO DIMM
              Vendor Serial (SN): NO DIMM
              HW Revision: 0
              Form Factor: Unknown
              Type: Unknown
              Capacity (MB): Unknown
              Clock: Unknown
              Latency: 2917376161116564280513419804672.000000
              Width: 14400

Environment

• Cisco Firepower 4100 Security Appliance (FPR-4115-K9)

• First seen on FXOS Version: 2.14(1.167)

• FTD Version: 7.4.7.50 (running), 6.4.0.102 (startup)

• High Availability Configuration with FMC Management

• Memory Configuration: 12 x 16GB DDR4 Modules at 2666 MHz

• Affected DIMM: DIMM_A1 in Memory Slot 1

Resolution

1. Perform chassis reboot to attempt memory fault recovery:

fxos# scope chassis
fxos /chassis # reboot
fxos /chassis* # commit-buffer

2. After allotting time for a full system boot, re-verify the component status fault status in the FXOS CLI and Chassis Manager UI.

3. If DIMM fault persists after full reboot, hardware replacement is required via Cisco RMA.

Cause

The diagnostics confirmed a critical memory subsystem fault where the DDR4_P1_A1_ECC sensor threshold was crossed, indicating complete module failure after an unexpected chassis reboot. The DIMM A1 reported an "Inoperable" status with all SPD (Serial Presence Detect) data unreadable, confirming irreversible hardware failure rather than a transient error that cannot be recovered by a graceful reboot. The memory fault prevented the security module and FTD logical instance from initializing properly, resulting in the "Inoperable" chassis state that persisted after chassis reboot.

Related Content

• Replace Faulty Unit in Secure Firewall Threat Defense High Availability

• Create and Manage Logical Devices in FXOS Chassis Manager

• Cisco Firepower 4100 Hardware Installation Guide

• FXOS Troubleshooting Guide

• Cisco Technical Support & Downloads