BugZero | Cisco BugID CSCvb34556 - Cat3850 - 10G member of Ether-channel with LACP is...

Cisco - Defect ID: CSCvb34556

Cat3850 - 10G member of Ether-channel with LACP is continuously flapping

Cisco - Defect ID: CSCvb34556

Cat3850 - 10G member of Ether-channel with LACP is continuously flapping

Last updated on February 12th, 2026

BugZero Risk Score
8.0 High

Overall: 8.0

Severity: 8.2

Lifecycle: 9.1

Popularity: 6.9

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Bug Details

Description

Symptom

+Line protocol from 10G interface member of Etherchannel, configured with LACP, is constantly flapping almost every 3-5 min aprox. +No errors or drops on physical interfaces. +"show lacp counters" shows almost the double of packets sent compared with packets received. +10G Interface that is flapping is in the Standby switch.

Conditions

+WS-C3850-12XS or WS-C3850-24XS running IOS Version 3.7.4. +LACP configured. +Identified in 10G interfaces.

Workaround

+Etherchannel configuration to "Mode on". +Downgrade to IOS Version 3.7.3 or below.

Further Problem Description

Change history

2026-01-13 Added: 16.3.2, 16.3.3, 16.3.3a, 16.3.4, 16.3.5, 16.3.5a, 16.3.5b, 16.3.5c, 16.3.6, 16.3.7, 16.3.8, 16.3.9, 16.4.1, 16.4.2, 16.4.3, 16.5.1, 16.5.1a, 16.5.1b, 16.5.2, 16.5.3, 16.6.1, 16.6.1a, 16.6.2, 16.6.2s, 16.6.3, 16.6.4, 16.6.4a, 16.6.4s, 16.6.5, 16.6.5a, 16.6.5b, 16.6.6, 16.6.7, 16.7.1, 16.7.1a, 16.7.1b, 16.7.2, 16.7.3, 16.7.4, 3.7.5E_ngwc

Links

Original Vendor Announcement

Relevant Products

Click on a version to see all relevant bugs

Affected versions:No known affected versions

Fixed versions: 16.3.2, 16.3.3, 16.3.3a, 16.3.4, 16.3.5, 16.3.5a, 16.3.5b, 16.3.5c, 16.3.6, 16.3.7, 16.3.8, 16.3.9, 16.4.1, 16.4.2, 16.4.3, 16.5.1, 16.5.1a, 16.5.1b, 16.5.2, 16.5.3, 16.6.1, 16.6.1a, 16.6.2, 16.6.2s, 16.6.3, 16.6.4, 16.6.4a, 16.6.4s, 16.6.5, 16.6.5a, 16.6.5b, 16.6.6, 16.6.7, 16.7.1, 16.7.1a, 16.7.1b, 16.7.2, 16.7.3, 16.7.4, 3.7.5E_ngwc

Relevant Products

Click on a version to see all relevant bugs

Affected versions:No known affected versions

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Cisco - Defect ID: CSCvb34556

Cat3850 - 10G member of Ether-channel with LACP is continuously flapping

Cisco - Defect ID: CSCvb34556

Cat3850 - 10G member of Ether-channel with LACP is continuously flapping

Last updated on February 12th, 2026

BugZero Risk Score8.0 High

Bug Details

Symptom

Conditions

Workaround

Further Problem Description

Links

Top Cisco Defects

Ready to prevent the next vendor outage?

BugZero Risk Score
8.0 High