Field Notice: FN70252 - Inaccurate 'CDP-4-DUPLEX_MISMATCH' Messages Are Logged on AP Switchports - Software Upgrade Recommended

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Updated:October 4, 2023

Document ID:FN70252

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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 Software Product	Affected Release	Affected Release Number	Comments
Cisco Mobility Express	8.2	8.2.100.0, 8.2.110.0, 8.2.111.0, 8.2.121.0, 8.2.130.0, 8.2.141.0, 8.2.151.0, 8.2.160.0, 8.2.161.0, 8.2.164.0, 8.2.166.0
Cisco Mobility Express	8.3	8.3.102.0, 8.3.104.64, 8.3.111.0, 8.3.112.0, 8.3.121.0, 8.3.122.0, 8.3.130.0, 8.3.131.0, 8.3.132.0, 8.3.133.0, 8.3.140.0, 8.3.141.0, 8.3.143.0	8.3.102.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.104.64: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.111.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.112.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.121.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.122.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.130.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.131.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.132.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.133.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.140.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.141.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.143.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected.
Cisco Mobility Express	8.5	8.5.103.0, 8.5.105.0
Wireless LAN Controller Software	8.2	8.2.100.0, 8.2.110.0, 8.2.111.0, 8.2.121.0, 8.2.130.0, 8.2.141.0, 8.2.151.0, 8.2.160.0, 8.2.161.0, 8.2.164.0, 8.2.166.0
Wireless LAN Controller Software	8.3	8.3.102.0, 8.3.111.0, 8.3.112.0, 8.3.121.0, 8.3.122.0, 8.3.130.0, 8.3.131.0, 8.3.132.0, 8.3.133.0, 8.3.140.0, 8.3.141.0, 8.3.143.0	8.3.102.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.111.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.112.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.121.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.122.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.130.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.131.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.132.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.133.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.140.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.141.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected. 8.3.143.0: For 8.3.140.0 and later, only 2800, 3800 and 1560 APs are affected.
Wireless LAN Controller Software	8.5	8.5.103.0, 8.5.105.0

Defect Information

Defect ID	Headline
CSCve98689	Repeated CDP-4-DUPLEX_MISMATCH is observed when Cisco Wave 2 APs are connected to Cisco switch
CSCvi02106	Cisco 2800, 3800, 1560 APs: when connected to a Cisco Switch CDP-4-DUPLEX_MISMATCH log is seen

Problem Description

Cisco switches that have Wave 2 access points (APs) connected when they run the affected software might show 'CDP-4-DUPLEX_MISMATCH' messages.

Background

This is cosmetic only and not an actual duplex mismatch. Due to a software issue in the AP, half-duplex is reported in Cisco Discovery Protocol (CDP) which results in these warning messages.

Problem Symptom

You might see "CDP-4-DUPLEX_MISMATCH" messages on a Cisco switch that refer to a port where a Wave 2 AP is connected. By default, these messages are logged every 60 seconds per port. This could cause the syslog buffers to fill up and lose more important messages.

Workaround/Solution

Workaround

In order to prevent these duplex mismatch warning messages from being captured in your syslogs, complete one of these workarounds:

Disable CDP and enable Link Layer Discovery Protocol (LLDP) (if the switch supports it) on the switch port connected to the AP.
Note: For the AP to power on its radios without CDP, enable LLDP for power management.
```
config terminal
lldp run
interface <interface connected to the AP>
no cdp enable
end
```
Reduce the syslogging threshold to capture only those events that are severity 3 or greater (Severity 0 is the highest severity).

config terminal

logging {buffered/trap/console} 3

end

This will prevent syslog buffer overflow related to the excessive logging of the severity 4 duplex mismatch warning messages."

Solution

Upgrade to a code version not affected by these bugs:

Versions 8.2.170.0 and 8.5.110.0 and later have the Cisco bug ID CSCve98689 fix, and are not affected by Cisco bug ID CSCvi02106.
Version 8.3.14x.0 has the Cisco bug ID CSCve98689 fix, but is affected by Cisco bug ID CSCvi02106.
Version 8.3MR4esc, available from the Technical Assistance Center (TAC), has a fix for Cisco bug ID CSCvi02106.

How to Identify Affected Products

Look in the switch syslog to see if it reports a duplex mismatch on the interface connected to a Wave 2 AP. Wave 2 APs include 1800, 1810, 1815, 1830, 1850, 2800, 3800, 1540, and 1560 series. All Wave 2 APs are affected by Cisco bug ID CSCve98689. Only 2800, 3800 and 1560 series APs are affected by Cisco bug ID CSCvi02106.

Example

*Jun 13 16:16:24.164: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/2 (not half duplex), with AP1 GigabitEthernet0 (half duplex). *Jun 13 16:17:16.809: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet1/0/2 (not half duplex), with AP1 GigabitEthernet0 (half duplex).

Revision History

Version	Description	Section	Date
1.1	Updated the Products Affected Section to Include All 8.2 Versions Earlier Than 8.2.170 and All 8.3 Versions Earlier Than 8.3.140	—	2018-SEP-24
1.0	Initial Release	—	2018-JUL-31

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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