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vMX interface ordering

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  • 1.  vMX interface ordering

    Posted 05-17-2017 18:07

    Hi, I've recently experienced strange problem.


    This is vMX deployment on ESXi.

    When vMX VMs (vcp, vfpc) are deployed, two interfaces (vnics) are created by default.

    The first one is for fxp0 and the second one is for internal re-pfe communication.

    If I add one more vnic, this will be used as ge-0/0/0.

    As I add more vnics, the interface ordering is preserved as listed below.


    vnic1 - fxp0

    vnic2 - internal link

    vnic3 - ge-0/0/0

    vnic4 - ge-0/0/1

    vnic5 - ge-0/0/2

    vnic6 - ge-0/0/3


    If I add one more vnic, then interfaces are no longer in order.


    vnic1 - fxp0

    vnic2 - internal link

    vnic3 - ge-0/0/0

    vnic4 - ge-0/0/2

    vnic5 - ge-0/0/3

    vnic6 - ge-0/0/4

    vnic7 - ge-0/0/1


    Anybody experienced similar issue?

    Thanks in advance.


  • 2.  RE: vMX interface ordering
    Best Answer

    Posted 05-18-2017 06:45

    The mismatching was caused by the way how ESXi maps PCI slot numbers to guest-visible PCI bus topology (see https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2047927 for details).


    It's not a vMX specific issue, if you bring up a Linux VM with 10 network interface, you will see the similar behaviour.

  • 3.  RE: vMX interface ordering

    Posted 06-05-2017 10:55

    I've experienced the same thing with vMX on Workstation 12. It's exactly the same order that you have listed when I add 5 more vnics. I've just lived with it or modified the config file to redo the vnic to interface mapping.

  • 4.  RE: vMX interface ordering

    Posted 07-27-2017 21:19

    Ran into the same issue. This problem happens when adding vmxnet interfaces for your revenue ports. It is a problem with Vmware  pciBridge load balancing mechanism and  it is not present with e1000 type. Yet in my experience e1000 driver is poorly performs (PFE errors, interfaces flapping, etc) when adding max number of interfaces.


    Found the solution in the SRX tech library doc:




    Keep br-int and ext e1000 for both RE and PFE or they will not sync and fxp0 will be inaccessable.


    Then follow the guide for adding vmxnet ports. Worked like a charm.

  • 5.  RE: vMX interface ordering

    Posted 08-29-2017 05:39

    I just took an email on this issue, and the vSRX link has now been removed from j-net. I did I quick blog post on it - http://matt.dinham.net/interface-ordering-vmware/