Running tcpdump in a VM improves performance of scp transfers

Solution In Progress - Updated -


  • When tcpdump is running in a KVM VM and then a transfer with scp is performed the performance is double that found when tcpdump is not running.
  • Does not matter if tcpdump is run with promiscuous mode on or off (-p).
  • Turning on promiscuous mode but not running tcpdump does not increase performance.
  • Only affects scp. Transfers with dd and netcat are always just as fast as the performance found when running scp with tcpdump.


  • Red Hat Enterprise Linux 5
  • KVM
  • tcpdump
  • scp
  • HP ProLiant DL580 G7

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