PI Routeur

Routeur Raspberry Pi 2 : WAN DHCP, LAN 10.11.11.0/24, DHCP & NAT

Objectif

• eth0 (WAN) en **client DHCP** – adresse et passerelle obtenues du réseau amont.
• eth1 (USB‑Ethernet) en **IP statique 10.11.11.1/24** – **passerelle** du LAN.
• **Serveur DHCP** via dnsmasq : plage 10.11.11.100–10.11.11.200, passerelle 10.11.11.1.
• **Routage IPv4** activé et **NAT** (masquerade) avec nftables.

Prérequis

• Raspberry Pi 2 avec Raspberry Pi OS.
• Un adaptateur USB‑Ethernet pour le LAN (nommé eth1 ou enx<MAC>).
• Accès sudo.

Identifier les interfaces

ip -o link show | awk -F': ' '/eth|enx/{print $2}'

Moi j'ai

eth0
eth1

Configuration réseau

Bookworm (NetworkManager)

sudo nmcli con add type ethernet ifname eth0 con-name wan ipv4.method auto ipv6.method ignore
sudo nmcli con add type ethernet ifname eth1 con-name lan ipv4.method manual ipv4.addresses 10.11.11.1/24 ipv4.never-default yes ipv6.method ignore
sudo nmcli con up wan
sudo nmcli con up lan

Anciennes versions (dhcpcd)

sudo nano /etc/dhcpcd.conf
interface eth1
static ip_address=10.11.11.1/24
sudo systemctl restart dhcpcd

DHCP (dnsmasq)

sudo apt install -y dnsmasq
sudo tee /etc/dnsmasq.d/lan.conf >/dev/null <<'EOF'
interface=eth1
bind-interfaces
domain-needed
bogus-priv
dhcp-range=10.11.11.100,10.11.11.200,255.255.255.0,24h
dhcp-option=option:router,10.11.11.1
EOF
sudo systemctl enable --now dnsmasq

Routage IPv4 et NAT

echo 'net.ipv4.ip_forward=1' | sudo tee /etc/sysctl.d/99-ip-forward.conf
sudo sysctl -p /etc/sysctl.d/99-ip-forward.conf

nftables

sudo tee /etc/nftables.conf >/dev/null <<'EOF'
flush ruleset
table inet filter {
  chain input   { type filter hook input priority 0; policy accept; }
  chain output  { type filter hook output priority 0; policy accept; }
  chain forward { type filter hook forward priority 0; policy drop;
    ct state established,related accept
    iif "eth1" oif "eth0" accept
  }
}
table ip nat {
  chain postrouting { type nat hook postrouting priority 100;
    oif "eth0" masquerade
  }
}
EOF
sudo systemctl enable --now nftables

Tests

ip addr show eth0
ip addr show eth1
journalctl -u dnsmasq | tail -n 50
ping 1.1.1.1
curl -s https://ifconfig.me

Script complet

#!/bin/bash
# Routeur Pi 2 – WAN DHCP (eth0), LAN 10.11.11.0/24 (eth1), DHCP & NAT
set -e
sudo nmcli con add type ethernet ifname eth0 con-name wan ipv4.method auto ipv6.method ignore
sudo nmcli con add type ethernet ifname eth1 con-name lan ipv4.method manual ipv4.addresses 10.11.11.1/24 ipv4.never-default yes ipv6.method ignore
sudo nmcli con up wan; sudo nmcli con up lan
sudo apt install -y dnsmasq
sudo tee /etc/dnsmasq.d/lan.conf >/dev/null <<'EOF'
interface=eth1
bind-interfaces
domain-needed
bogus-priv
dhcp-range=10.11.11.100,10.11.11.200,255.255.255.0,24h
dhcp-option=option:router,10.11.11.1
EOF
sudo systemctl enable --now dnsmasq
echo 'net.ipv4.ip_forward=1' | sudo tee /etc/sysctl.d/99-ip-forward.conf
sudo sysctl -p /etc/sysctl.d/99-ip-forward.conf
sudo tee /etc/nftables.conf >/dev/null <<'EOF'
flush ruleset
table inet filter {
  chain input   { type filter hook input priority 0; policy accept; }
  chain output  { type filter hook output priority 0; policy accept; }
  chain forward { type filter hook forward priority 0; policy drop;
    ct state established,related accept
    iif "eth1" oif "eth0" accept
  }
}
table ip nat {
  chain postrouting { type nat hook postrouting priority 100;
    oif "eth0" masquerade
  }
}
EOF
sudo systemctl enable --now nftables