Why is network traffic slow on a RHEL VM running on VMware?

Solution In Progress - Updated -

Issue

  • Why are transfers intermittently slow via VMware to Netbackup storage?

  • Why is general network traffic slow on a RHEL VMware VM?

  • We found that port forward outgoing traffic get delayed by around 1 second intermittently. Tcpdump captures on the network by means of vSwitch port mirroring for normal and delayed port forward traffic were collected for investigation.
    We found some "fragmentation needed" packet return to external IP.

  • Running tcpdump on the inteface puts the interface into promiscuous mode makes packets flow well or makes the NFS client problem go away

Environment

  • Red Hat Enterprise Linux 5 and 6
  • VMware
  • The vmxnet3 driver

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