[Buildbot] #3183: fix network "spottiness" on new infra

[Buildbot trac]

#3183: fix network "spottiness" on new infra
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Reporter:  dustin    |       Owner:
    Type:  defect    |      Status:  new
Priority:  critical  |   Milestone:  sys - other
 Version:            |  Resolution:
Keywords:            |
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Comment (by dustin):

 That MAC belongs to `service4.rtems.org`, which should be in port-group 7
 *only*, not port-group 33.  Port-group 33 is vm1.  So our best guess is
 that they are accidentally cross-wired.  But it's hard to see why that
 would cause the symptoms we're seeing here.

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Ticket URL: <http://trac.buildbot.net/ticket/3183#comment:29>
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