After update and restart, VLAG switches may Stop passing traffic - IBM Flex


RETAIN tip: H21561


vLAGed EN4093 Scalable Switches may stop passing traffic during the code update process.
(where vLAG = Virtual Link Aggregation)

Switches in a vLAG that are running firmware 7.3.x (or prior) may become unresponsive and stop passing traffic when one (1) of the switches is updated to firmware 7.5.x (or later) and then restarted.

The issue occurs when an updated switch restarts. The following error message example is seen in the switch log of the switch not yet updated:

May 31 18:34:08 xxxxxxxxx ERROR vlag: vLAG between different platforms is not supported

Affected configurations

The system is configured with one or more of the following IBM Options:

  • IBM Flex System Fabric EN4093 10 Gb Scalable Switch, any model

This tip is not system specific.

This tip is not software specific.


Update the firmware on all scalable switches at the same time. For example, update the firmware on both switches, then restart both switches at the same time.

This will minimize the switch outage.

Additional information

This vLAG issue is due to an incompatibility that exists between the two (2) firmware levels, and requires that multiple switches in a vLAG be at the same firmware level.

As the problem exists in firmware 7.3.x (and prior), it cannot be compensated for in future codes. Therefore, no new code will be released for this issue.

Applicable countries and regions


Document id:  MIGR-5093430
Last modified:  2013-08-27
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