Field Notice: FN - 63949 - Cisco Catalyst 3650 T2 Series Stack Cable Might Cause Intermittent Link Failures - Replace on Failure

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.

Revision History

Products Affected

Defect Information

Problem Description

Some faulty Cisco Catalyst 3650 T2 Series stack cables might cause intermittent link failures between the switch members or break the full ring. This might result in the loss of connectivity to both the primary and standby switches, which can result in a reset to the switch stack.

Background

Cisco has discovered that a limited number of STACK-T2-50CM, STACK-T2-1M, and STACK-T2-3M cables were contaminated. The root cause is determined to be surface contamination of the gold edge finger contacts on the end of the cables.

Problem Symptom

When a Catalyst 3650 Series switch (C3650) is booted up with an affected T2 stack cable, random increments in the #Changes to LinkOK column of the show switch stack-ports summary command output might be observed. Additionally, the switch stack might reset due to the loss of connectivity to the active and standby switches.

Note: The increments in the Changes to LinkOK counter is normal during switch/stack boot up and when a new switch member is inserted. The problem symptom for this Field Notice is only observed after a full ring has been established and no new switch is added to the stack.

How to Identify the Issue

After a C3650 switch stack is reset and the full ring has been established, verify whether there are any increments in the Changes to LinkOK counter in the show switch stack-port summary command output. This example illustrates a faulty stack cable between Port 2 of Switch 3 and Port 1 of Switch 4 (highlighted in bold):

Switch#show switch stack-ports summary
Sw#/Port#  Port Status  Neighbor  Cable Length   Link OK   Link Active   Sync OK   #Changes to LinkOK  In Loopback
-------------------------------------------------------------------------------------------------------------------
1/1        OK           2         50cm           Yes       Yes             Yes       1                   No
1/2        OK           5         300cm          Yes       Yes             Yes       1                   No
2/1        OK           3         50cm           Yes       Yes             Yes       1                   No
2/2        OK           1         50cm           Yes       Yes             Yes       1                   No
3/1        OK           4         50cm           Yes       Yes             Yes       1                   No
3/2        OK           2         50cm           Yes       Yes             Yes       3                   No
4/1        OK           5         50cm           Yes       Yes             Yes       4                   No
4/2        OK           3         50cm           Yes       Yes             Yes       1                   No
5/1        OK           1         300cm          Yes       Yes             Yes       1                   No
5/2        OK           4         50cm           Yes       Yes             Yes       1                   No
Switch#

In order to manually verify whether a T2 stack cable is suspect, ensure that the thumbscrews are finger-tight, and then wiggle the cable connector head where it connects into the switch. If the Changes to LinkOK counter increments specific to that link, then the T2 stack cable should be replaced.

Workaround/Solution

In order to proactively determine whether a C3650 T2 Series stack cable is affected by this issue, use the Serial Number Validation Tool for FN #63949.

If a C3650 T2 Series stack cable exhibits abnormal behavior as per this Field Notice or is identified as Affected in the Serial Number Validation Tool, request the appropriate C3650 T2 Series stack cable hardware replacement.

How To Identify Affected Products

In order to obtain the serial number of a C3650 T2 Series stack cable, perform a physical inspection of the Serial Number label on the cable:

For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods:

• Open a service request on Cisco.com
• By email
• By telephone

Receive Email Notification For New Field Notices

Cisco Notification Service—Set up a profile to receive email updates about reliability, safety, network security, and end-of-sale issues for the Cisco products you specify.