ansiblings/cubes/network/wifi/access-point

WiFi Access Point Cube (NetworkManager)

Configures a Linux device as a WiFi Access Point using NetworkManager's nmcli command. This approach allows the device to simultaneously act as an AP AND remain connected to another WiFi network as a client.

Key Features

• ✅ Dual WiFi Mode: Acts as AP while staying connected to another WiFi
• ✅ Modern Approach: Uses NetworkManager (nmcli) instead of hostapd
• ✅ Auto-start: Configured to start on boot
• ✅ IP Sharing: Built-in internet sharing with ipv4.method shared
• ✅ Simple Configuration: Minimal parameters, maximum functionality
• ✅ Supports 2.4GHz and 5GHz bands

Requirements

• Device with WiFi capability (e.g., Raspberry Pi 4/5)
• NetworkManager installed and running
• WiFi hardware that supports AP mode

Configuration Parameters

Required

• SSID: WiFi network name (1-32 characters)
• PASSWORD: WPA2 password (8-63 characters)

Optional (with defaults)

• NETWORK_DEVICE: WiFi interface to use (wlan0 default)
• BAND: Frequency band - 2.4GHz or 5GHz (auto-detected from current connection if not specified)
• CHANNEL: WiFi channel (auto-detected from current connection if not specified)
  • 2.4GHz: 1-14
  • 5GHz: 36-165
• IP_ADDRESS: AP gateway address (192.168.50.1 default)
• CONNECTION_NAME: NetworkManager connection name (net:wifi:ap default)

Example Usage

Basic Configuration

{
  "SSID": "MyHomeWiFi",
  "PASSWORD": "SecurePass123"
}

Advanced Configuration (5GHz with specific channel)

{
  "SSID": "FastWiFi5G",
  "PASSWORD": "SuperSecure456",
  "NETWORK_DEVICE": "wlan1",
  "BAND": "5GHz",
  "CHANNEL": 36,
  "IP_ADDRESS": "10.0.0.1",
  "CONNECTION_NAME": "my-hotspot"
}

Auto-Detection Configuration

When BAND and CHANNEL are not specified, the script will automatically detect the current AP's band and channel using iw dev <interface> link and use those values for the new hotspot. This is useful when you want the hotspot to operate on the same band/channel as your existing connection to avoid interference.

{
  "SSID": "MyAutoAP",
  "PASSWORD": "SecurePass123"
}

What This Cube Does

1. Installs NetworkManager (if not present)
2. Enables NetworkManager service and ensures it's running
3. Auto-detects current AP settings using iw dev <interface> link to find the band and channel
4. Creates WiFi hotspot using nmcli with auto-detected or specified settings
5. Configures IP sharing with ipv4.method shared (automatic DHCP + NAT)
6. Enables IP forwarding for internet routing
7. Sets autoconnect so the AP starts on boot

How It Works (Dual WiFi Mode)

Simultaneous AP + Client Mode

Hardware Support Required:

• Your WiFi hardware must support simultaneous AP+STA (Station) mode
• Most modern WiFi chips support this (e.g., Raspberry Pi 4/5, Intel WiFi cards)
• Older hardware may not support it (e.g., Raspberry Pi 3B and earlier have limitations)

How NetworkManager Handles It:

1. Single Interface (e.g., wlan0):

   • If hardware supports AP+STA: ✅ Both client and AP run on same interface
   • If hardware doesn't support it: ⚠️ Client connection may be dropped

2. Multiple Interfaces (e.g., wlan0 + wlan1):

   • NetworkManager will use one for client, another for AP
   • Always works regardless of hardware capabilities

Example Scenario (Raspberry Pi 4):

[Internet] <--WiFi--> [RPi4 wlan0 (Client+AP)] <--WiFi--> [Devices connect to AP]

How to Check Hardware Support:

iw list | grep -A 10 "valid interface combinations"

Look for: * #{ managed } <= 1, #{ AP } <= 1 or * #{ managed, AP } <= 2

NetworkManager will:

• Share internet from any available source (WiFi client, Ethernet, cellular, etc.)
• Automatically handle routing and NAT
• Try to maintain client connection if hardware supports it

Post-Installation

After deployment, the device will:

• ✅ Broadcast the WiFi network with your SSID
• ✅ Accept connections with your password
• ✅ Assign IP addresses to connected clients (via built-in DHCP)
• ✅ Share internet connection from any available interface
• ✅ Auto-start the AP on every boot
• ✅ Maintain client WiFi connection (if connected to another network)

Managing the Hotspot

View connection status

nmcli connection show

Stop the hotspot

sudo nmcli connection down net:wifi:ap

Start the hotspot

sudo nmcli connection up net:wifi:ap

Disable autostart

sudo nmcli connection modify net:wifi:ap connection.autoconnect no

Delete the hotspot

sudo nmcli connection delete net:wifi:ap

Troubleshooting

AP doesn't start

• Check NetworkManager status: sudo systemctl status NetworkManager
• Verify WiFi interface exists: nmcli device status
• Check if AP mode is supported: iw list | grep -A 10 "Supported interface modes"

Can't connect to AP

• Verify password is correct (8+ characters)
• Check channel compatibility with your devices
• Try switching between 2.4GHz and 5GHz bands

No internet on clients

• Verify host device has internet: ping 8.8.8.8
• Check IP forwarding: sysctl net.ipv4.ip_forward
• NetworkManager should handle NAT automatically with ipv4.method shared

Hotspot conflicts with client WiFi

• This shouldn't happen with NetworkManager

• If it does, check if hardware supports simultaneous AP+STA mode:

  iw list | grep "valid interface combinations"
  

Advantages Over Traditional Approach

Feature	Traditional (hostapd)	NetworkManager (nmcli)
Dual WiFi	❌ No (conflicts with wpa_supplicant)	✅ Yes (AP + client simultaneously)
Configuration	Complex (multiple files)	Simple (one command)
DHCP	Manual (dnsmasq)	Automatic
NAT	Manual (iptables)	Automatic
Management	Multiple services	Single service
Dependencies	hostapd, dnsmasq, iptables	NetworkManager only

Security Notes

• Always use a strong password (minimum 8 characters)
• WPA2 encryption is automatically enabled
• NetworkManager handles firewall rules automatically

Compatibility

Tested on:

• Raspberry Pi 4/5 with built-in WiFi
• Ubuntu/Debian-based systems with NetworkManager
• Devices with WiFi hardware supporting AP mode

Note: Older Raspberry Pi models (3B and earlier) may have limitations with simultaneous AP + client mode due to hardware constraints.

Troubleshooting

sudo nmcli con add type wifi con-name MyHotspot ifname wlan0 mode ap ssid YourNewAP ipv4.method shared wifi-sec.key-mgmt wpa-psk wifi-sec.psk "YourNewPassword"
sudo nmcli con up MyHotspot
sudo nmcli con down MyHotspot
sudo nmcli con mod MyHotspot wifi.band <band> wifi.channel <channel_number>
# Find the currently used band and channel
iw dev wlan0 link