0 Replies Latest reply on Jun 16, 2020 4:20 PM by MrTimshel

    Help me understand why "Hosts large ping test" sends packets larger than the end-point's interface MTU

    MrTimshel Lurker

      Hi,

       

      I'm involved in commissioning a Stretched vSAN Cluster and we are currently troubleshooting a failed 'Hosts large ping test' on the Witness server's network paths to vSAN Cluster nodes.

       

      The current configuration follows the Witness Traffic Separation design - as illustrated in this doc Witness Traffic Separation (WTS) | vSAN Stretched Cluster Guide | VMware

       

      I understand that the 'Hosts large ping test' identifies whether MTU mismatch exists in the network path. However, this is only an issue when a 9000 byte packet is sent. Anything less than that is not an issue.

       

      To me it seems that a client application would have to ignore/override the network interface's MTU setting and fragment the packet at transmission for this have a real-world impact. Perhaps this is possible - in which case; Is this something that the vSAN witness server will encounter and, if so, why?

       

      What is the relevance of the test sending confirming MTU mismatch with packets exceeding the MTU of the end-point's interfaces?