This how-to describes how to setup raspberry pi as router and NAT, DHCP and firewall. Wifi adapter is used as WAN interface, Ethernet adapter is used as LAN interface for local network. Rasbian lite was used for this setup, version 2019-04-08 (Stretch).
This interface is configured in automatic dhcp mode.
This interface has static configuration. Internal network is 192.168.40.0/24 This interface is default gateway for this network.
in /etc/sysctl.conf setup variable net.ipv4.ip_forward to 1
net.ipv4.ip_forward = 1
edit /etc/network/interfaces, so it looks like this:
# interfaces(5) file used by ifup(8) and ifdown(8)
# Please note that this file is written to be used with dhcpcd
# For static IP, consult /etc/dhcpcd.conf and 'man dhcpcd.conf'
# Include files from /etc/network/interfaces.d:
source-directory /etc/network/interfaces.d
auto eth0
iface eth0 inet static
address 192.168.40.1
netmask 255.255.255.0
auto wlan0
allow-hotplug wlan0
iface wlan0 inet dhcp
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
iface default inet dhcp
Add wifi network setup into /etc/wpa_supplicant/wpa_supplicant.conf
network={
ssid="network-name"
psk="supersercretpassword"
}
Install dhcp server sudo apt-get install isc-dhcp-server
Then create and edit a new file /etc/dhcp/dhcpd.conf containing:
option domain-name "example.org";
option domain-name-servers 8.8.8.8, 8.8.4.4;
default-lease-time 600;
max-lease-time 7200;
ddns-update-style none;
subnet 192.168.40.0 netmask 255.255.255.0 {
range 192.168.40.10 192.168.40.250;
option routers 192.168.40.1;
}
Also edit the file /etc/default/isc-dhcp-server to add the line:
INTERFACESv4="eth0"
INTERFACESv6=""
To control the DHCP server, use:
sudo systemctl restart isc-dhcp-server
sudo systemctl status isc-dhcp-server