Raspberry Pi 4 have onboard wireless networking.

I built Raspberry Pi Wi-Fi 5 Router, so I’ll noted that its technical point of view and how to build it.

Specification

H/W : Raspberry Pi 4 Model B 2GB RAM

OS : Raspberry Pi OS 32bit

Technical Point of View

How to build the system

Installing access point daemon “hostapd” and DNS server software”dnsmasq”.

sudo apt install hostapd dnsmasq

Changing static IP address.

sudo nano /etc/dhcpcd.conf

Going to end of file and editing it like the following.

interface wlan0
static ip_address=192.168.5.1/24
nohook wpa_supplicant

Restarting DHCP

sudo systemctl restart dhcpcd

Configurating hostapd.

sudo nano /etc/hostapd/hostapd.conf

interface=wlan0
driver=nl80211
# a is IEEE802.11a(5GHz)
hw_mode=a
channel=36
wmm_enabled=0
macaddr_acl=0
auth_algs=1
ssid=raspberrypi4_router
ignore_broadcast_ssid=0
wpa=2
wpa_passphrase=passphrase
wpa_key_mgmt=WPA-PSK
wpa_pairwise=CCMP
ieee80211d=1
ieee80211h=1
ieee80211n=1
require_ht=1
ht_capab=[HT40-][SHORT-GI-20][SHORT-GI-40]
ieee80211ac=1
vht_capab=[SHORT-GI-80][HTC-VHT]
require_vht=1
vht_oper_chwidth=1
vht_oper_centr_freq_seg0_idx=42

Addtionaly, editing access point daemon startup configuration.

sudo nano /etc/default/hostapd

Replacing line with #DAEMON_CONF like the following.

DAEMON_CONF="/etc/hostapd/hostapd.conf"

Configurating dnsmasq

sudo nano /etc/dnsmasq.conf

interface=wlan0
dhcp-range=192.168.5.100,192.168.5.150,255.255.255.0,24h

Starting installed software

sudo systemctl unmask hostapd
sudo systemctl enable hostapd
sudo systemctl start hostapd
sudo systemctl enable dnsmasq
sudo systemctl start dnsmasq

Setting NAPT( IP Masquerade )

sudo nano /etc/sysctl.conf

Changing uncomment the following line

net.ipv4.ip_forward=1

Setting and saving

sudo iptables -t nat -A  POSTROUTING -o eth0 -j MASQUERADE

sudo apt install iptables-persistent
sudo /etc/init.d/iptables-persistent save
sudo /etc/init.d/iptables-persistent reload

Connecting your wireless devices to Raspberry Pi access point.

Completed !!