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Bridged_Wireless_Access_Point.md

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Bridged Wireless Access Point

A bridged wireless access point setup works within an existing ethernet network to extend the network to WiFi capable computers and devices in areas where the WiFi signal is weak or otherwise does not meet expectations.

Known issues:

  • WPA3-SAE operation is not testing good at this time and is disabled.

This document is for WiFi adapters based on the following chipsets

rtl8811au, rtl8821au

2021-02-25

Tested Setup

  • Raspberry Pi 4B (4gb)

  • Raspberry Pi OS (2021-01-11) (32 bit) (kernel 5.10.11-v7l+)

  • Raspberry Pi Onboard WiFi disabled

  • USB WiFi Adapter based on the rtl8811au chipset

  • WiFi Adapter Driver - https://github.com/morrownr/8821au

  • Ethernet connection providing internet

    • Ethernet cables are CAT 6
    • Internet is Fiber-optic at 1 Gbps up and 1 Gbps down
Steps
  1. Disable Raspberry Pi onboard WiFi.
$ sudo nano /boot/config.txt

Add

dtoverlay=disable-wifi
  1. Install the driver for the WiFi adapter.

Follow the instructions at this site

https://github.com/morrownr/8821au.git

  1. Change driver options (to allow high speed operation.)
$ sudo nano /etc/modprobe.d/8821au.conf

rtw_vht_enable=2      (enable 80 Mhz channel width)
  1. Update system.
$ sudo apt update

$ sudo apt full-upgrade

$ sudo reboot
  1. Install needed package.
$ sudo apt install hostapd
  1. Enable the wireless access point service and set it to start when your Raspberry Pi boots.
$ sudo systemctl unmask hostapd

$ sudo systemctl enable hostapd
  1. Add a bridge network device named br0 by creating a file using the following command, with the contents below.
$ sudo nano /etc/systemd/network/bridge-br0.netdev

File contents

[NetDev]
Name=br0
Kind=bridge
  1. Determine the names of the network interfaces.
$ ip link show

Note: If the interface names are not eth0 and wlan0, then the interface names used in your system will have to replace eth0 and wlan0 during the remainder of this document.

  1. Bridge the Ethernet network with the wireless network, first add the built-in Ethernet interface ( eth0 ) as a bridge member by creating the following file.
$ sudo nano /etc/systemd/network/br0-member-eth0.network

File contents

[Match]
Name=eth0

[Network]
Bridge=br0
  1. Enable the systemd-networkd service to create and populate the bridge when your Raspberry Pi boots.
$ sudo systemctl enable systemd-networkd
  1. Block the eth0 and wlan0 interfaces from being processed, and let dhcpcd configure only br0 via DHCP.
$ sudo nano /etc/dhcpcd.conf

Add the following line above the first interface xxx line, if any

denyinterfaces wlan0 eth0

Go to the end of the file and add the following line

interface br0
  1. To ensure WiFi radio is not blocked on your Raspberry Pi, execute the following command.
$ sudo rfkill unblock wlan
  1. Create the hostapd configuration file.
$ sudo nano /etc/hostapd/hostapd.conf

File contents

# /etc/hostapd/hostapd.conf
# https://w1.fi/hostapd/
# 2g, 5g, a/b/g/n/ac
# 2021-02-20

# Needs to match your system
interface=wlan0

bridge=br0
driver=nl80211
ctrl_interface=/var/run/hostapd
ctrl_interface_group=0

# Change as desired
ssid=pi

# Change as required
country_code=US

# Enable DFS channels
ieee80211d=1
ieee80211h=1

# 2g (b/g/n)
#hw_mode=g
#channel=6
#
# 5g (a/n/ac)
hw_mode=a
channel=36
#channel=149

beacon_int=100
dtim_period=1
max_num_sta=32
macaddr_acl=0
ignore_broadcast_ssid=0
rts_threshold=2347
fragm_threshold=2346
send_probe_response=1

# Security
auth_algs=1
ignore_broadcast_ssid=0
wpa=2
wpa_pairwise=CCMP
# Change as desired
wpa_passphrase=raspberry
# WPA-2 AES
wpa_key_mgmt=WPA-PSK WPA-PSK-SHA256
# WPA-3 SAE
#wpa_key_mgmt=SAE
wpa_group_rekey=1800
rsn_pairwise=CCMP
# ieee80211w=2 is required for WPA-3 SAE
#ieee80211w=2
# If parameter is not set, 19 is the default value.
#sae_groups=19 20 21 25 26
#sae_require_mfp=1
# If parameter is not 9 set, 5 is the default value.
#sae_anti_clogging_threshold=10

# IEEE 802.11n
# 2g and 5g
ieee80211n=1
wmm_enabled=1
#
# Note: Capabilities can vary even between adapters with the same chipset
#
# 8811au
# 20 MHz channel width for band 1 - 2g
#ht_capab=[MAX-AMSDU-7935]
# 40 MHz channel width for band 2 - 5g
ht_capab=[HT40+][HT40-][MAX-AMSDU-7935]

# IEEE 802.11ac
# 5g
ieee80211ac=1
#
# Note: Capabilities can vary even between adapters with the same chipset
#
# 8811au
vht_capab=[MAX-MPDU-11454][SHORT-GI-80][SU-BEAMFORMEE][HTC-VHT]

# Turn on 80 MHz channel width
vht_oper_chwidth=1
#
# Use with channel 36
vht_oper_centr_freq_seg0_idx=42
#
# Use with channel 149
#vht_oper_centr_freq_seg0_idx=155

# Event logger
#logger_syslog=-1
#logger_syslog_level=2
#logger_stdout=-1
#logger_stdout_level=2

# WMM
#uapsd_advertisement_enabled=1
#wmm_ac_bk_cwmin=4
#wmm_ac_bk_cwmax=10
#wmm_ac_bk_aifs=7
#wmm_ac_bk_txop_limit=0
#wmm_ac_bk_acm=0
#wmm_ac_be_aifs=3
#wmm_ac_be_cwmin=4
#wmm_ac_be_cwmax=10
#wmm_ac_be_txop_limit=0
#wmm_ac_be_acm=0
#wmm_ac_vi_aifs=2
#wmm_ac_vi_cwmin=3
#wmm_ac_vi_cwmax=4
#wmm_ac_vi_txop_limit=94
#wmm_ac_vi_acm=0
#wmm_ac_vo_aifs=2
#wmm_ac_vo_cwmin=2
#wmm_ac_vo_cwmax=3
#wmm_ac_vo_txop_limit=47
#wmm_ac_vo_acm=0

# TX queue parameters
#tx_queue_data3_aifs=7
#tx_queue_data3_cwmin=15
#tx_queue_data3_cwmax=1023
#tx_queue_data3_burst=0
#tx_queue_data2_aifs=3
#tx_queue_data2_cwmin=15
#tx_queue_data2_cwmax=63
#tx_queue_data2_burst=0
#tx_queue_data1_aifs=1
#tx_queue_data1_cwmin=7
#tx_queue_data1_cwmax=15
#tx_queue_data1_burst=3.0
#tx_queue_data0_aifs=1
#tx_queue_data0_cwmin=3
#tx_queue_data0_cwmax=7
#tx_queue_data0_burst=1.5

# end of hostapd.conf
  1. Establish conf file and log file locations.
$ sudo nano /etc/default/hostapd

Add to bottom of file

DAEMON_CONF="/etc/hostapd/hostapd.conf"
DAEMON_OPTS="-d -K -f /home/pi/hostapd.log"
  1. Reboot the system.

$ sudo reboot

  1. Enjoy!