vSphere vNetwork

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  • 1.  DVS and kernel port issue

    Posted Aug 07, 2023 11:28 AM

    I'm setting up 2 hosts with dvS.

    The dVS has 2 Uplinks and we have configured 2 vmKernel ports for ISCSI traffic and bound each to only one uplink, the other set to unused.

    The problem is that it seems that only one, on each host, is working properly.

    When we tested the configuration by disabling one uplink at time, from the switch, we found that the with the first uplink UP is working, but with only the second Uplink it is not.

    From the switch side all the uplink ports for both the hosts are configured the same.

    The strange thing is also that even if the affected host cannot ping the Iscsi Portal anymore it doesn't lose access to the storage.


  • 2.  RE: DVS and kernel port issue

    Posted Aug 07, 2023 03:12 PM

    Which ESXi version do you have there? 

  • 3.  RE: DVS and kernel port issue

    Posted Aug 07, 2023 03:37 PM

    Hi there

    we run 8.01

  • 4.  RE: DVS and kernel port issue

    Posted Aug 07, 2023 05:13 PM

    Is it a single, or multiple subnet setup?
    Is the proper MTU configured from end-to-end?

    What you may want to check is to use vmkping from the hosts command line, which lets you specify the VMkernel port as well as the MTU, e.g. vmkping -I vmk1 -d -s 8972 target-ip


  • 5.  RE: DVS and kernel port issue

    Posted Aug 07, 2023 09:59 PM

    Ask you network team to send you the port config for each port. 

    Not sure of your setup, but in our environment, we have a different VLAN for each SCSI path. vmkping as mentioned is a good way of testing connectivity through each vmkernel interface like so:

    • vmkping -I vmk1 x.x.x.x (where vmk1 is the first iSCSI vmkernel port)
    • vmkping -I vmk2 y.y.y.y (where vmk2 is the second iSCSI vmkernel port)

    Where x.x.x.x and y.y.y.y are the iSCSI target IP addresses for each VLAN. Remember, if using multiple VLANs make sure you have 2 interfaces on the target configured with an IP address in each VLAN range too.

    If jumbo frames are configured, then as per post above, use -d -s 8972 as your ping test, where 9000 is the configured MTU on the switch.

    Its also a good idea to capture the switchport config for all of your network connections, as this is good to document, and can help you troubleshoot problems like this.


  • 6.  RE: DVS and kernel port issue

    Posted Aug 08, 2023 02:50 PM

    The setup is a single dVS with a Single Subnet space.

    2 vmk bound to each vmnik

    VMKPING to Storage

    It works with no problem when both or one specific NIC, the one bound to uplink1, are connected.

    When the NIC bound to uplink2 is the only connected the vmkping to storage doesn't work BUT the storage keeps to be accessible by the host. ALSO other vmk ( vmotion ) on different VLAN connected to the same dVS works fine ( even the vmkping ) 

    It seems something much related with the ISCSI virtual adapter binding