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Jumbo frames are supported only on VMxnet 3 and enhanced VMxnet

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VMXNET and VMXNET3 are the only adapters that works with Jumbo Frames.

vmxnet3If you trying to configure and use Jumbo frames to optimize your VI infrastructure, you should only use vmxnet (and vmxnet3) virtual adapters for that.

The other adapters seems to accept the configuration for the MTU, but they're not actually working like they should be. They're dropping frames which are larger than 1500. It means that you not gaining any throughput, but you're LOOSING speed there !!

This applys to those VMware ESX server versions:


VMware ESX 4.0.x
VMware ESXi 4.0.x Embedded
VMware ESXi 4.0.x Installable
VMware vCenter Server 4.0.x

In VMware KB article 1015556 it's said:

Adapters other than enhanced vmxnet (and vmxnet3) adapters, for example the E1000 adapter, cannot be used with jumbo frames. >Attempts to change the MTU appear to succeed but the adapter always drops frames larger than 1500 bytes.

Source: VMware KB 1015556

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Comments

  1. james says

    Thanks for confirming. I had to query this because the vcp5-dcv Official Cert Guide by vmware Press states not to use vmxnet3 on page 155 stating there is a bug with vmxnet3 and it states you should always use vmxnet2 or e1000 only. I thought the same as you and think the information in the book is not accurate. I mentioned to vmware anyway. Great book with the exception of this misleading information and I do not wish to put down the author but was merely querying this one section of the book.

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