Link state flapping may occur for Mellanox nmlx4_en drivers during vxlan port change in ESXi hosts

Products

• VMware vSphere ESXi

Issue/Introduction

• Link state will flap momentarily during vxlan port update.
• This behavior is seen with Mellanox Network Card MT27500/MT27520 Family [ConnectX-3/ConnectX-3 Pro]
• Mellanox NIC driver that is in use is nmlx4_en version 3.15.2.0 and newer.

The below observations can be made as symptoms:

• An ESXi host is experiencing traffic loss momentarily.
• All Virtual Machine traffic using a Mellanox adapter might experience traffic loss momentarily

The cause of the issue can be associated to:

• This is device limitation whenever vxlan port needs to be updated.
• The upgrade of a distributed switch, reconfiguration of vxlan UDP port can result in this behavior.

Resolution

It has been identified that the link state would restore automatically.