Introduction

The Alfa AWUS036ACH is a popular USB Wi-Fi adapter that uses the Realtek RTL8812AU chipset. While powerful, it can present several challenges when setting up on a Raspberry Pi, especially for features like monitor mode and packet injection. This guide provides a systematic approach to identify and fix common driver issues.

Table of Contents

1. Hardware Verification
2. Basic Installation Methods
3. Troubleshooting Common Issues
4. Advanced Configuration
5. Monitor Mode and Packet Injection
6. Power Issues
7. Kernel Compatibility
8. Additional Resources

Hardware Verification

Before proceeding with software troubleshooting, verify your hardware:

1. Confirm your adapter model: Ensure you have the genuine AWUS036ACH.

2. USB port functionality:

• The adapter requires significant power. Try connecting directly to the Raspberry Pi (not through a USB hub).
• If possible, use a USB 3.0 port for better performance.
• Use a high-quality USB cable.

3. Verify chipset detection:

lsusb

Look for ID 0bda:8812 (Realtek Semiconductor Corp. RTL8812AU).

4. Power Supply:

• Ensure your Raspberry Pi has an adequate power supply (at least 2.5A recommended).
• The adapter’s LED should light up when powered.

Basic Installation Methods

There are several approaches to install the driver. If one method fails, try an alternative.

Method 1: Using DKMS (Recommended)

DKMS ensures the driver is automatically rebuilt when the kernel is updated:

# Install prerequisites

sudo apt update
sudo apt upgrade
sudo apt-get install bc mokutil build-essential libelf-dev linux-headers-`uname -r` dkms git

# Clone the driver repository

git clone -b v5.6.4.2 https://github.com/aircrack-ng/rtl8812au.git
cd rtl8812au

# If using Raspberry Pi 3/4 with ARM64 architecture

sed -i 's/CONFIG_PLATFORM_I386_PC = y/CONFIG_PLATFORM_I386_PC = n/g' Makefile

sed -i 's/CONFIG_PLATFORM_ARM64_RPI = n/CONFIG_PLATFORM_ARM64_RPI = y/g' Makefile

# For older Raspberry Pi models (ARMv7)

sed -i 's/CONFIG_PLATFORM_I386_PC = y/CONFIG_PLATFORM_I386_PC = n/g' Makefile

sed -i 's/CONFIG_PLATFORM_ARM_RPI = n/CONFIG_PLATFORM_ARM_RPI = y/g' Makefile

# Install with DKMS

sudo make dkms_install

# Reboot

sudo reboot

Method 2: Using Morrownr’s Driver Repository

This is an alternative driver repository that’s often more up-to-date:

# Install prerequisites

sudo apt update && sudo apt upgrade

sudo apt-get install dkms

sudo apt install -y raspberrypi-kernel-headers build-essential bc dkms git

# Clone repository

mkdir -p ~/src

cd ~/src

git clone https://github.com/morrownr/8812au-20210629.git

cd ~/src/8812au-20210629

# Install driver

sudo ./install-driver.sh

If you encounter kernel header errors, modify the boot config:

sudo su
cd /boot
nano config.txt

Add the following line under the [pi4] section:

arm_64bit=0

Save (Ctrl+O, Enter), exit (Ctrl+X), then reboot:

sudo reboot

Troubleshooting Common Issues

Driver Not Loading

Check if the driver is loaded:

lsmod | grep 88

You should see 8812au or similar in the output.

If not loaded, try manual loading:

sudo modprobe 8812au

Check kernel logs for errors:

dmesg | grep -i rtl

Interface Not Appearing

List network interfaces:

ip a

Look for wlan1 (or similar) if you already have wlan0 for the built-in Wi-Fi.

If no interface appears:

sudo rmmod 8812au 
sudo modprobe 8812au

Reboot the system:

sudo reboot

Compilation Errors

Missing kernel headers:

sudo apt install raspberrypi-kernel-headers

Architecture mismatch errors:

For ARMv7:

export ARCH=arm 
sed -i 's/^MAKE="/MAKE="ARCH=arm\ /' dkms.conf

For ARM64:

export ARCH=arm64
sed -i 's/^MAKE="/MAKE="ARCH=arm64\ /' dkms.conf

Out of memory during compilation:

Increase swap space:

sudo nano /etc/dphys-swapfile

   # Change CONF_SWAPSIZE=100 to CONF_SWAPSIZE=2000

sudo /etc/init.d/dphys-swapfile restart

Advanced Configuration

LED Control

Control the LED behavior of the adapter:

# Disable LED blinking (0 = off, 1 = on)

echo "0" > /proc/net/rtl8812au/$(your_interface_name)/led_ctrl

# Check current setting

cat /proc/net/rtl8812au/$(your_interface_name)/led_ctrl

Alternatively, create a modprobe configuration:

echo "options 88XXau rtw_led_ctrl=0" | sudo tee /etc/modprobe.d/realtek-leds.conf

USB Mode Switching

Switch between USB 2.0/3.0 modes:

sudo rmmod 88XXau

sudo modprobe 88XXau rtw_switch_usb_mode=1  # 0=no switch, 1=USB2->USB3, 2=USB3->USB2

Disable MAC Address Randomization

If NetworkManager keeps changing your MAC address:

sudo nano /etc/NetworkManager/NetworkManager.conf

Add:

[device]

wifi.scan-rand-mac-address=no

Then restart NetworkManager:

sudo service NetworkManager restart

Monitor Mode and Packet Injection

These features are essential for network analysis and security testing.

Setting Up Monitor Mode

Kill potentially interfering processes:

sudo airmon-ng check kill

Set interface down:

sudo ip link set wlan1 down  # Replace wlan1 with your interface name

Set monitor mode:

sudo iw dev wlan1 set type monitor

Set interface up:

sudo ip link set wlan1 up

Verify monitor mode:

iwconfig wlan1

It should show “Mode: Monitor”.

Troubleshooting Monitor Mode

If monitor mode doesn’t work:

Try using airmon-ng instead:

sudo airmon-ng start wlan1

Check for interference:

sudo airmon-ng check

Kill any processes listed.

Manual mode setting:

sudo iwconfig wlan1 mode monitor

Check driver capability:

iw list

Look for “monitor” in supported interface modes.

Setting TX Power

Adjust transmission power (use with caution):

sudo iw wlan1 set txpower fixed 3000

Power Issues

The AWUS036ACH requires significant power, which can cause issues with the Raspberry Pi.

Check USB power management:

sudo iwconfig wlan1 power off

Disable power savings:

sudo nano /etc/modprobe.d/8812au.conf

Add:

options 8812au rtw_power_mgnt=0 rtw_enusbss=0

Use a powered USB hub if direct connection fails.

Kernel Compatibility

The driver might have compatibility issues with newer kernels.

Check current kernel version:

uname -a

Prepare kernel for module compilation:

cd /usr/src/kernel

sudo git clean -fdx && sudo make bcm2711_defconfig && sudo make modules_prepareFor severe kernel incompatibility issues, consider using an older kernel version:

sudo apt install raspberrypi-kernel=1.20201126-1

(Replace with appropriate version if needed)

Additional Resources

• Official GitHub Repository
• Morrownr’s Driver Repository
• Alfa Networks Support Page
• Rokland Driver Support Page

Conclusion

The AWUS036ACH can work well with Raspberry Pi, but requires some configuration. If one method fails, try an alternative approach, as driver compatibility can vary between different Raspberry Pi models and OS versions.

Remember that kernel updates might break your driver installation, requiring you to reinstall the driver. Using DKMS can help minimize this issue by automatically rebuilding the driver when the kernel is updated.

What happens when you have multiple hosts on your network with the same mdns name?

mDNS handles naming collisions through a process called “probing and announcing” defined in RFC 6762. Here’s how it works:

Collision Detection Process:

• When a device wants to claim a name (like “ansibledest.local”), it first “probes” by sending queries for that name
• If another device already has that name, it responds, indicating a collision
• The new device must then choose a different name, typically by appending a number (ansibledest-2.local, ansibledest-3.local, etc.)
• This process repeats until an unclaimed name is found

In practice- I haven’t seen this behavior, exactly. The devices all come online and if you run the hostname command, each of them thinks they’re Spartacus. You have to ping a specific ip address to get the updated mdns name in your cache. Annoying:

RFC 6762 told me I was good!

Well- I know the host is online apparently. I wonder what happens if I ping the hostname again-

It works. hooray.

Identifying duplicate mdns entries

You can use the avahi-browse command to see what’s up on your network. The hosts are apparently doing some kind of incremental naming- but not in a way that provides tcp/ip utility.

avahi-browse -at | grep ansibledest*
+ wlp0s20f3 IPv6 ansibledest-4 [mac:addy:du:jour]             Workstation          local
+ wlp0s20f3 IPv6 ansibledest [mac:addy:du:jour]              Workstation          local
+ wlp0s20f3 IPv6 ansibledest-3 [mac:addy:du:jour]             Workstation          local
+ wlp0s20f3 IPv6 ansibledest-3 [mac:addy:du:jour]             Workstation          local
+ wlp0s20f3 IPv6 ansibledest [mac:addy:du:jour]               Workstation          local
+ wlp0s20f3 IPv6 ansibledest-2 [mac:addy:du:jour]             Workstation          local
+ wlp0s20f3 IPv6 ansibledest-2 [mac:addy:du:jour]             Workstation          local
+ wlp0s20f3 IPv4 ansibledest-4 [mac:addy:du:jour]             Workstation          local
+ wlp0s20f3 IPv4 ansibledest-2 [mac:addy:du:jour]             Workstation          local
+ wlp0s20f3 IPv4 ansibledest-3 [mac:addy:du:jour]             Workstation          local
+ wlp0s20f3 IPv4 ansibledest-2 [mac:addy:du:jour]             Workstation          local
+ wlp0s20f3 IPv4 ansibledest [mac:addy:du:jour]               Workstation          local
+ wlp0s20f3 IPv4 ansibledest [[mac:addy:du:jour]               Workstation          local

Tenets for handling outrage inducing content on social media:

Most people don’t see the world through a True/False filter but an Us/Them filter

• https://www.leaderonomics.com/articles/personal/do-you-get-along-with-others
• https://x.com/michaelmalice/status/1738694461469741411

Introspection is uncommon

30-50% of people you meet don’t have an inner monologue.

The Internet Rewards Narcissists

When you see someone talking shit about a stranger online, remember that narcissists use “Splitting” to expel a narcissist’s bad behavior from their own memory.

Opinions != Expertise

The founding fathers were concerned about giving the right people the right to vote. They wanted to index on property owners to ensure that outcomes were dictated by citizens with a “stake in the game”. They were right to be concerned with the intentions of outsiders. Consider if the person whinging has a stake in the game- or is someone who is espousing their feelings about how other people should live.

Dangerous Outcomes Feared by the Founding Fathers

• “Tyranny of the Majority” – Madison’s great fear in Federalist No. 10, where majority factions could oppress minorities and violate property rights
• Mob Rule and Instability – Hamilton worried about “temporary delusion” of the masses (Federalist No. 68)
• Wealth Redistribution – John Adams wrote: “The moment the idea is admitted into society that property is not as sacred as the laws of God… anarchy and tyranny commence” (Defence of the Constitutions, 1787)
• Election of Demagogues – The Electoral College was partly designed as a safeguard against this (Hamilton, Federalist No. 68)

Public schools are funnels for producing useful idiots.

The public education community has long forgone any semblance of objectivity and fairness. The education system employs people who want a safe career with a pension and ample vacation. The incentives of public education are for teachers who comply and teach compliance. This attracts teachers who drive students towards voting for policies that produce government jobs which forego excellence and accountability.

Disagreeableness is undesirable

Most people generally prefer to get along to go along.

Seeking what is true is not seeking what is desirable.

Cruelty is easier than compassion.

It is the weak who are cruel. Gentleness is only to be expected from the strong.

Here’s a common error to run into:


TASK [essential : Run the equivilent of apt-get update] **************************************************************
fatal: [ansibledest.local]: FAILED! => {“changed”: false, “msg”: “Failed to update apt cache: W:Updating from such a repository can’t be done securely, and is therefore disabled by default., W:See apt-secure(8) manpage for repository creation and user configuration details., W:GPG error: http://hostname.local:3142/raspbian.raspberrypi.org/raspbian bookworm InRelease: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY 9165938D90FDDD2E, E:The repository ‘http://hostname.local:3142/raspbian.raspberrypi.org/raspbian bookworm InRelease’ is not signed.”}

This can be solved by adding the following to your ansible playbooks:


– name: Add raspbian public signing key
apt_key:
keyserver: keyserver.ubuntu.com
id: 9165938D90FDDD2E
state: present

– name: Update apt cache
apt:
update_cache: yes

Listing Creating, modifying and deleting connections

List your connections:

nmcli connection show

Rename a connection that you want to skip IPv6 on:

sudo nmcli connection modify "JoinMe-AP" 802-11-wireless.mode ap 802-11-wireless.ssid JoinMe 802-11-wireless.band bg 802-11-wireless-security.key-mgmt none connection.interface-name wlan1 ipv4.method shared ipv6.method ignore

Delete a connection by it’s name:

 sudo nmcli connection delete "JoinMe-AP" # Clean slate (optional)

“Which vulnerabilities should we fix first?”

This question often leads to confusion, especially for those deeply involved in security. Every company has unique priorities which makes it challenging to create a one-size-fits-all approach.
Don’t lose hope- here’s a straightforward method inspired by musicians’ mnemonics to help you feel confident that you considered everything that’s important when assessing a vulnerability’s priority.

Every Engineer Always Prioritizes Data By Evaluating Risk

This phrase breaks down into key factors to consider:

• E – Exploitability: How easily can someone exploit the vulnerability?
• E – Exposure: Is the system connected to the internet or internal?
• A – Access Required: What level of access does an attacker need?
• P – Patch Difficulty: How hard is it to fix the issue?
• D – Data Sensitivity: Does the system handle sensitive information?
• B – Business Impact: What effect would an exploit have on the company?
• E – Environmental Mitigations: Are there existing defenses in place?
• R – Raw CVSS Score: What is the base severity score?

Achieving zero vulnerabilities is ideal but often unrealistic. Resources are often limited, so it’s crucial that we prioritize effectively. This mnemonic helps me ensure I’ve considered the whole set of aspects that should be reviewed when deciding which vulnerabilities to address first.

By evaluating each factor, you can make informed decisions that balance risk and resource allocation, leading to a more secure and efficient system.