While browsing the (unofficial) VMware Reddit this morning and came across a thread where the OP was asking for a recommendation on USB network adapters that can be used with ESXi with their Intel NUC, which many replied with their recommendations and a pointer over to the USB Network Native Driver for ESXi Fling, which would be required if you are using one of the supported chipsets.
The community already covered all the basics and I did not have anything to add until I saw the following comment:
To my knowledge at least, there are zero drivers for USB network interfaces without using a fling.
Although this was certainly true a few years back, that the only way for ESXi to see a USB network adapter was to first install the USB Network Native Driver, this is technically no longer accurate due to some recent enhancements with ESXi that may not be very well known.
With the release of ESXi 7.0, a USB CDCE (Communication Device Class Ethernet) driver was added to enable support for hardware platforms that now leverages a Virtual EEM (Ethernet Emulation Module) for their out-of-band (OOB) management interface, which was the primary motivation for this enhancement.
One interesting and beneficial side effect of this enhancement is that for any USB network adapters that conforms to the CDCE specification, they would automatically get claimed by ESXi and show up as an available network interface demonstrated in my homelab with the screenshot below.
This can certainly benefit VMware Homelabs, especially if you have a hardware platform that does not currently have the required driver installed for networking. In fact, this capability was also heavily relied upon during the early days of developing the ESXi on Arm Fling, as the onboard network adapter was not fully supported yet.
Given the primary use case for introducing the CDCE driver was for OOB management, one thing you will notice is that speed will always negotiate to 100Mbps and that is currently hardcoded. Once you have installed ESXi, customers are still recommend to install the USB Network Native Driver for ESXi Fling as that will give you better performance but also broader support for other USB based network adapters.
CDCE USB Network Adapters
As mentioned earlier, I regularly rely on this capability and I personally own two different USB network adapters that support the CDCE specification which customers may find interesting, especially as the Reddit OP was looking for some options.
Option 1: Cable Matters USB-A to 1GbE Adapter (Pictured Left)
Option 2: Belkin USB-C to 1GbE Adapter (Pictured Right)
Both of these USB network adapters uses a Realtek 8153 chipset and it is possible that other RTL8153-based USB network adapters could also be supported with the CDCE driver, these two are confirmed to be functional. In addition, once you install the USB Network Native Driver for ESXi Fling, these adapters will automatically be claimed by that driver and will negotiate at 1GbE instead of 100Mbps.