Technical information

Performance Best Practices for VMware vSphere 4.0
34 VMware, Inc.
For VMXNET, the default number of receive and transmit buffers is 100 each, with the maximum possible
being 128. For Enhanced VMXNET, the default number of receive and transmit buffers are 150 and 256,
respectively, with the maximum possible receive buffers being 512. You can alter these settings by
changing the buffer size defaults in the .vmx (configuration) files for the affected virtual machines. For
additional information see KB article 1428, listed in “Related Publications” on page 8.
For VMXNET3 and E1000, the default number of receive and transmit buffers are controlled by the guest
driver, with the maximum possible for both being 4096. For Linux, the values for both VMXNET3 and
E1000 can be changed from within the guest by using ethtool. In Windows, the values for E1000 can be
changed in the device properties window.