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RTL8811AU Driver Guide (AWUS036ACS)

Quick Summary: The Realtek RTL8811AU is the 1×1 AC433 chipset inside the 55 mm AWUS036ACS — the pocket-sized monitor-mode companion. Like its big brother the RTL8812AU, it needs the community rtl8811au driver via DKMS, but the build is identical.

Concept: same family, one stream​

The RTL8811AU is essentially the 1×1 variant of the RTL8812AU family: one spatial stream, 433 Mbps max on 5 GHz, lower power draw, smaller board. ALFA wraps it in the tiny ACS body with one external 2 dBi RP-SMA antenna — you get the classic ALFA pen-testing behavior in a package that hides in a pencil case.

Driver-wise, nothing changes from the RTL8812AU story: no in-kernel driver with monitor support, so we use the community 8821au-20210708 DKMS driver. Note the driver also covers the RTL8821AU variant, so do not panic if your dkms status shows the same module name on similar dongles.

Prerequisites​

  • Linux (Ubuntu 20.04+ / Kali / Debian)
  • sudo apt install -y build-essential dkms git
  • sudo access
  • AWUS036ACS

Step 1: Clone and build​

cd /opt
sudo git clone https://github.com/morrownr/8821au-20210708.git
cd 8821au-20210708
sudo sh install-driver.sh

Expected output:

DKMS: install completed.

Step 2: Load and verify​

sudo modprobe 8821au
iw dev

Expected output: an Interface wlan0 (or wlan1) line. If the adapter only shows up after re-plug, add the module to auto-load:

echo 8821au | sudo tee /etc/modules-load.d/alfa.conf

Step 3: Monitor mode + injection​

sudo airmon-ng check kill
sudo airmon-ng start wlan0
sudo aireplay-ng --test wlan0mon

Expected output:

PHY	Interface	Driver		Chipset
phy0	wlan0		8821au		Realtek Semiconductor Corp. RTL8811AU
...
12:34:56  Injection is working!
12:34:56  30/30:  100%

Step 4: Back to normal​

sudo airmon-ng stop wlan0mon
sudo systemctl restart NetworkManager

Troubleshooting​

SymptomCauseFix
DKMS build failsMissing headers / too-new kernelsudo apt install linux-headers-$(uname -r); cd 8821au-20210708 && git pull && sudo sh install-driver.sh
Interface only in managed modeKernel stub rtl8811au grabbed itecho "blacklist rtl8811au" | sudo tee /etc/modprobe.d/alfa-8811au.conf; reboot
Injection 0/30Empty channelsudo iw wlan0mon set channel 6; test near an AP
Throughput lower than expected1×1 radio (AC433) — hardware limitNot a bug; expect ~150–250 Mbps real-world on 5 GHz
Not detected after rebootModule not auto-loadedAdd 8821au to /etc/modules-load.d/alfa.conf

References​