How to configure a WLAN gateway

1. How to configure a wireless gateway

A wireless gateway routes packets from a wireless LAN to wired network (Ethernet)

For this example of configuration, the setup is :

• wlan0: wireless interface connected to SSID_NETWORK with DHCP
• eth0: ethernet interface with static IP which also have a DHCPserver on it
• forward of packet are activated between the two network interfaces.

1.1. Configure wireless interface

 cat /lib/systemd/network/wlan0.network
 [Match]
 Name=wlan0
  
 [Network]
 DHCP=ipv4
 IPForward=ipv4

IPForward

permit to forward all network packet from wireless network to other network.

• Configure wireless interface for SSID_NETWORK network:

 mkdir -p /etc/wpa_supplicant/
 echo "ctrl_interface=/var/run/wpa_supplicant" > /etc/wpa_supplicant/wpa_supplicant-wlan0.conf
 echo "eapol_version=1" >> /etc/wpa_supplicant/wpa_supplicant-wlan0.conf
 echo "ap_scan=1" >> /etc/wpa_supplicant/wpa_supplicant-wlan0.conf
 echo "fast_reauth=1" >> /etc/wpa_supplicant/wpa_supplicant-wlan0.conf
 echo "" >> /etc/wpa_supplicant/wpa_supplicant-wlan0.conf
 wpa_passphrase SSID_NETWORK PASSWORD_NETWORK >> /etc/wpa_supplicant/wpa_supplicant-wlan0.conf
 or
 wpa_passphrase SSID_NETWORK  >> /etc/wpa_supplicant/wpa_supplicant-wlan0.conf

Where SSID_NETWORK PASSWORD_NETWORK correspond to the SSID and password of wireless network.

• Enable the wireless configuration (to be take into account after reboot):

 systemctl enable wpa_supplicant@wlan0.service
         systemctl restart systemd-networkd.service
         systemctl restart wpa_supplicant@wlan0.service

Dynamic host configuration pProtocol (see https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol for more details)