VMware: Migrating Management(Mgmt) vmk to DVS/VDS fails when moving both vmnic and vmk at the same time.

Summary:
Quite simple, had a script to move physical nics to DVS/VDS w/ management vmk at the same time.  Typically this works w/o issue, but for some reason kept failing.  The answer was dead simple...

Resolution/Workaround:
  1. Spanning Tree Enabled?
    • Enable portfast on the switch ports.
  • Or
  1. Spanning Tree not available?
    1. Move one physical link at a time (assuming more than one physical link available)
    2. Wait for uplink on DVS to come online, then move management/mgmt vmk
Explanation:
Basically, the switch ports that the ESXi servers were uplinked to did not have 'portfast' (physical switchside config) enabled.  Without 'portfast', when moving a physical nic from a standard vSwitch (or vice versa), there is a negotiation downtime the host incurs as the switch/host essentially renegotiates the connectivity.  It's a short window (5-10 sec) that the port goes 'offline', but it's enough for the migration of vmk and physical nics at the same time to fail.

Example PowerCLI Snippet:

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