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KB40163 - High hits per second and throughput levels with low number of users on virtual appliances

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Last Modified Date3/3/2016 11:37 PM
If large receive offload (LRO) is enabled, virtual appliances may experience the following symptoms:
  • High hits per second,
  • High throughput levels
  • High CPU levels 
  • Slower than expected performance
  • Large number of jumbo packet drops in tcpdump (packet capture) on internal or external interfaces
Problem or Goal
By default, LRO (Large Receive Offload) is not enabled for virtual appliances.  However, this can be enabled on the virtual machine hosts.  This can cause a problem if receiving a large fragmented piece of data from a VM on the same ESX.  
LRO will reassemble incoming packets data to reduce the number of packets handled by the network stack.  As a result, when the virtual appliance receives these packets, they are seen as jumbo packet and dropped.  For more information how LRO works, please refer to
There are two possible resolutions:
  1. Disable LRO for the entire host on the VMWare server.  Please refer to
  2. You can change the interface type on the virtual appliance from VMXNET3 (default) to E1000.  E1000 interfaces do not support LRO.
Related Links
Attachment 1 
Created ByTravis Bradbury



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