Field Notice: FN74164 - A Limited Subset of Memory Modules in Cisco 8540 and 5520 Wireless Controllers May Fail Prematurely, Resulting in System Instability or Degraded Function - Hardware Upgrade Available
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Notice
THIS FIELD NOTICE IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTY OF MERCHANTABILITY. YOUR USE OF THE INFORMATION ON THE FIELD NOTICE OR MATERIALS LINKED FROM THE FIELD NOTICE IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS FIELD NOTICE AT ANY TIME.
Products Affected
| Affected Product Name | Description | Comments |
|---|---|---|
| AIR-CT5520-50-K9 | ^Cisco 5520 Wireless Controller supporting 50 APs w/rack kit | |
| AIR-CT5520-CA-K9 | ^Cisco 5520 Wireless Controller for Service Depot | |
| AIR-CT5520-K9 | ^Cisco 5520 Wireless Controller w/rack mounting kit | |
| AIR-CT5520-K9-RF | Cisco5520WirelessController w/rackMountng kit REMANUFACTURED | |
| AIR-CT5520-K9-WS | Cisco5520 Wireless Contlr w/rack mounting kit REFURBISHED | |
| AIR-CT8540-K9 | ^Cisco 8540 Wireless Controller with rack mouting kit | |
| C1-AIR-CT5520-K9 | ^Cisco ONE - 5520 Wireless Controller w/rack mounting kit | |
| EDU-CT5520-K9 | ^Cisco 5520 Wireless Controller w/rack mounting kit K12 |
Defect Information
| Defect ID | Headline |
| CSCwb83995 | Uncorrectable ECC errors in DIMMs in 5520, 8540 controllers |
Problem Description
Some Cisco 8540 and 5520 Wireless Controllers can experience memory failure.
A failed dual in-line memory module (DIMM) may either prevent the host wireless LAN controller (WLC) from loading and running its operating system or cause the host WLC to operate in a degraded state because less system memory is available after the failed DIMM is disabled.
Background
A specific subset of affected WLCs identified by serial number were assembled with DIMMs that were subsequently determined to have a higher than expected probability of failing prematurely ahead of their normally predicted lifespan.
A problematic DIMM can cause its host WLC to fail to boot or to run below its capabilities.
Observable memory failures may be classified as correctable or uncorrectable DIMM errors, as described in the following sections.
Correctable DIMM Errors
DIMMs with correctable errors are not disabled and are available for the operating system to use. The total memory and effective memory are the same (memory mirroring is taken into account). These correctable errors are reported in Cisco Integrated Management Controller (IMC) as degraded once they exceed predetermined error thresholds.
Uncorrectable DIMM Errors
Uncorrectable errors generally cannot be fixed and may make it impossible for the application or operating system to continue execution. DIMMs with uncorrectable errors will be disabled if DIMM blacklisting is enabled or if the DIMM fails upon reboot during BIOS power-on self-test (POST), and the operating system will not see that memory. Cisco IMC support will be inoperable for the DIMM.
Correctable memory errors are not unexpected, even in unaffected DIMMs. Symptomatic DIMMs may initially experience correctable memory errors that degrade over time into uncorrectable memory errors. However, it is also possible for symptomatic DIMMs to fail initially due to uncorrectable memory errors.
This issue has been resolved, and affected units in Cisco RMA depots have been purged.
Problem Symptom
When a symptomatic WLC resets, reboots, or is power cycled, failed DIMMs may be disabled. DIMMs that fail the memory test portion of the POST will not be made available to the WLC operating system. The symptomatic WLC may not be able to load and run its operating system if there is not enough system memory available. If the symptomatic WLC can still load and run its operating system, system performance will likely be impaired, which will be indicated by slow responsiveness, system instability, or both.
Note: POST error messages may only be observed at the system console. Consult the appropriate WLC user guides for the location of the system console port and the associated interface requirements.
Overall WLC system status is visually indicated by the system status LED that is located on the front panel of the device. The LED signals indicate the following device states:
- Green On: The system is in normal operating condition.
- Amber On: The system is in a degraded operational state.
- Amber Blinking: The system is in a critical fault state.
On a symptomatic WLC with one or more failed DIMMs, the system status LED will change from green to amber (steady or blinking). Use the following steps to check Cisco IMC on the symptomatic WLC to confirm that the indicated system issue is related to a failed DIMM and to identify which DIMM is problematic:
- Consult the appropriate WLC user guides for the location of the WLC management port and the associated interface requirements.
- In Cisco IMC, check the Overall Server Status display in the upper left corner of the window, which will indicate the presence of a system fault on a symptomatic WLC.
- Click the Server tab in the left pane.
- Choose Faults and Logs to see a fault summary. Review the fault entries for conditions that indicate a failed DIMM.
- In the Server tab, choose Inventory. In the upper portion of the Inventory window, click the Memory tab to see which DIMM sockets contain failed DIMMs.
Note: Cisco IMC windows, tabs, and menu options may vary slightly among WLCs as they are dependent on the specific Cisco IMC release that is installed on each WLC. Therefore, the Cisco IMC screen examples shown in the following screenshots are for general guidance purposes only and are provided as aids in troubleshooting WLC DIMM failures:
Workaround/Solution
Customers who have products identified as affected by serial number validation should order replacement DIMMs using the instructions in the Upgrade Program section of this field notice. Do not open a service request (SR) to seek a replacement.
Once a customer has received the replacement DIMMs, they should use the instructions in the following documents to replace the DIMMs.
Cisco 8540 Wireless Controller
The Replacing DIMMs section of the Cisco UCS C240 M4 Server Installation and Service Guide.
Note: All four (qty = 4) DIMMs that are located at reference designators A1, B1, C1, and D1 should be replaced together.
Cisco 5520 Wireless Controller
The Replacing DIMMs section of the Cisco UCS C220 M4 Server Installation and Service Guide.
Note: Both (qty = 2) of the DIMMs that are located at reference designators A1 and B1 should be replaced together.
Serial Number Validation
Cisco provides the Serial Number Validation Tool to verify whether a device is impacted by this issue. To check the device, enter the serial number in the Serial Number Validation Tool.
Important: For security reasons, you must click the Serial Number Validation Tool link that is provided in this section. Do not copy and paste the link into a browser. Use of the Serial Number Validation Tool URL external to this field notice will fail.
Upgrade Program Information
Support Case Manager (SCM) must be used for ordering replacement parts for this Field Notice. To open SCM in a new tab, click the following link:
https://mycase.cloudapps.cisco.com/fieldnotice?fn=FN74164
SCM will validate eligibility and ensure that a request for a particular serial number has not already been submitted. If there is already a request, SCM will indicate RMA already submitted and NOT eligible for replacement.
Provide the following information:
- Affected serial numbers. Note that a serial number entitlement check may be performed.
- One ship-to address per request.
- Service Request number (SR#). This is not required, but if one exists, enter it for better tracking purposes.
Order entry supports up to 50 serial numbers per request. For more than 50, submit additional requests.
Revision History
| Version | Description | Section | Date |
| 1.0 | Initial Release | — | 2024-SEP-27 |
For More Information
For further assistance or for more information about this field notice, contact the Cisco Technical Assistance Center (TAC) using one of the following methods:
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