It Shows Up But Won't Pass Through - The ESXi USB WiFi Trap That Catches Everyone

**“It Shows Up… But Won’t Pass Through” — The ESXi USB WiFi Trap That Catches Everyone** On paper, this should’ve been simple. Plug in a USB WiFi adapter. Enable USB passthrough on **ESXi 8.0.3**. Attach it to a VM. Done. Instead, you’re staring at this: - Realtek RTL8188GU shows up in `lsusb` - It’s detected as **Driver CDROM Mode** - `esxcli hardware usb passthrough device list` says: `Enabled: false` `Can Connect to VM: no (passthrough disabled)` - You enable it - Add the USB quirk (`UQ_NET_IGNORE`) - Reboot And it still comes back disabled . That’s frustrating. But here’s the hard truth: this isn’t a configuration problem. It’s a platform limitation problem. --- ## What’s Actually Happening Your adapter: ``` 0bda:1a2b Realtek RTL8188GU 802.11n WLAN Adapter (Driver CDROM Mode) ``` That “Driver CDROM Mode” part is the key. Many Realtek USB WiFi adapters boot in a **mass storage mode first**. They present themselves as a fake CD-ROM containing Windows drivers. After the driver loads (on Windows), they switch into actual WiFi mode. ESXi does not handle this mode-switching behavior gracefully. Even worse: ESXi is extremely selective about USB device passthrough support. As someone replied bluntly: > Just because ESXi has USB passthrough does not mean any USB device will function — only devices on the USB HCL will function . And USB WiFi adapters? Almost never on the HCL. --- ## Why Your `UQ_NET_IGNORE` Didn’t Fix It You tried: ``` esxcli system settings advanced set -o /USB/quirks -s 0xbda:0x1a2b:0:0xffff:UQ_NET_IGNORE ``` That tells ESXi: “Don’t try to treat this as a USB NIC.” Which is correct. But it doesn’t fix: - The device being in CDROM mode - ESXi’s USB stack limitations - The fact that this class of device often isn’t supported for passthrough at all That’s why after reboot it still shows: ``` Enabled: false Can Connect to VM: no (passthrough disabled) ``` The host USB stack is still claiming it. --- ## The Bigger Reality: ESXi + USB WiFi Is Almost Always a Dead End Let’s zoom out. ESXi is designed for: - Datacenter NICs - Storage devices - Supported USB controllers It is **not designed to pass consumer USB WiFi adapters into VMs**. Even if you get it connected: - Performance is unpredictable - USB resets break connectivity - Reboots can detach it - Some chipsets never fully enumerate correctly You’re fighting the hypervisor’s design philosophy. --- ## The Only Two Paths That Might Work ### Option 1: Pass Through the Entire USB Controller (PCI Passthrough) Instead of USB device passthrough, passthrough the entire USB controller: 1. Go to **Host → Hardware → PCI Devices** 2. Find the USB controller 3. Enable passthrough 4. Reboot 5. Add PCI device to VM This sometimes works because: - The VM handles the USB stack directly - ESXi stops interfering But: - The whole USB controller is now owned by the VM - Everything plugged into that controller disappears from the host - Not all motherboards isolate USB controllers cleanly Still, this is your best shot . --- ### Option 2: Stop Using USB WiFi I know. Not what you want to hear. But this is usually the right answer. If your goal is: - Giving a VM WiFi access - Isolating traffic - Lab testing There are better approaches: - Use a wired uplink and VLAN segmentation - Use a small travel router as a WiFi bridge - Add a supported PCIe WiFi card and passthrough that - Use a separate physical box as a WiFi client and route traffic Trying to make ESXi behave like a desktop hypervisor is a painful road. --- ## The Realtek-Specific Problem Realtek USB chipsets are notorious for: - Weird enumeration behavior - Mode switching - Vendor-specific quirks - Poor Linux-level driver behavior Even on Linux hosts, people fight these adapters. On ESXi? You’re stacking incompatibility on top of incompatibility. --- ## Why It Keeps Showing Disabled After Reboot Notice how your device moved from: ``` Bus 1 Device 9 ``` to: ``` Bus 1 Device 3 ``` after reboot . That means: - USB topology re-enumerated - Device address changed - Your passthrough binding isn’t sticking That’s another red flag that ESXi isn’t happy owning this device. --- ## The Honest Answer Can you make this work? Maybe. If: - You passthrough the entire USB controller - The chipset doesn’t need mode switching - The VM OS handles it correctly - You don’t care about reliability Will this ever be production-stable? No. Not with that adapter. Not on ESXi. --- ## If This Is a Lab If this is just a home lab and you want to experiment: 1. Try PCI passthrough of USB controller 2. Test inside a Linux VM 3. If it fails, don’t sink more time into it Because the issue isn’t your commands. It’s the platform’s design constraints. --- ## Bottom Line You didn’t misconfigure it. You hit the boundary of what ESXi is meant to support. USB passthrough exists. But USB WiFi adapters — especially Realtek ones that boot in CDROM mode — are rarely compatible. If you want this clean and stable: Use proper networking hardware. Or passthrough an entire controller and accept the trade-offs. Anything else is going to feel like wrestling the hypervisor — and it usually wins.