How can I be connected at 10Gb when I only have 1Gb adapters in my hosts?

In this scenario you have an ESXi host with 1Gb physical adapters, and a virtual machine with the guest network speed showing connected at 10Gbps.

The host configuration looks like this;

1Gbps-uplinks

But the guest VM shows this;

10gbps-speed

This is rather confusing at first, especially considering that you don’t have any 10Gb interfaces in your hosts.

So how is this possible?

If you think about the virtual networking and how this VM is connected, then it makes perfect sense. The VM has a VMXNET3 adapter (see KB1001805 for adapter types) with the VM Tools installed and is connected to a virtual switch and since both of these components understand 10Gb so it’s expected behaviour.

The same would apply in a scenario with physical servers, you would see the speed that your server is connected to the physical switch.

I always find it easier to understand with visuals so sketched this up to help explain;

VMXNET3-Overview

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Author: Jon Munday

An independent IT contractor with a strong focus on VMware virtualisation and infrastructure operations. I am inspired by technology, not afraid to question the status quo and balance my professional commitments with entertaining my three awesome kids (Ashton, Oliver and Lara).

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