How to Set Up a Tunneled Wi-Fi Hotspot on Raspberry Pi OS Bookworm with WireGuard and NetworkManager

This guide updates our earlier tutorial for Debian 12 Bookworm on Raspberry Pi. In this architecture, the Raspberry Pi connects to upstream internet via Ethernet (eth0), establishes an encrypted WireGuard VPN tunnel (wg0), and broadcasts a secure Wi-Fi access point on wlan0. All client traffic connected to the hotspot is policy-routed strictly through the WireGuard tunnel.

Modern Bookworm Architecture: NetworkManager replaces dhcpcd and leverages the built-in dnsmasq-base plugin for DHCP and DNS caching, eliminating the need for standalone services like isc-dhcp-server.

1. Create the Wi-Fi Hotspot Profile in NetworkManager

Create a hotspot connection in the Raspberry Pi desktop Network GUI or via nmcli. Set the hotspot subnet to 10.0.1.1/24, enable auto-connect, and set MTU to 1420.

To enforce robust WPA2-only (RSN/AES) authentication and disable legacy WPA1:

nmcli con modify "Wi-Fi Hot" 802-11-wireless-security.proto rsn

2. Configure Policy Routing Table

Create a dedicated routing table for hotspot clients (subnet 10.0.1.0/24):

echo "200 INET2" | sudo tee -a /etc/iproute2/rt_tables

3. WireGuard Configuration (/etc/wireguard/wg0.conf)

Configure WireGuard with policy rules and MSS clamping to ensure seamless MTU handling through the tunnel:

[Interface]
PrivateKey = YOUR_PRIVATE_KEY
Address = 10.10.0.6/24
PostUp = iptables -t nat -A POSTROUTING -o wg0 -j MASQUERADE; ip rule add from 10.0.1.0/24 table INET2 priority 100; ip route add default dev wg0 table INET2; ip route add 8.8.8.8/32 dev wg0; ip route add 8.8.4.4/32 dev wg0; iptables -t mangle -A FORWARD -o wg0 -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu; iptables -t mangle -A FORWARD -i wg0 -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu; ip route flush cache
PreDown = iptables -t nat -D POSTROUTING -o wg0 -j MASQUERADE; ip rule del from 10.0.1.0/24 table INET2 priority 100; ip route del default dev wg0 table INET2; ip route del 8.8.8.8/32 dev wg0; ip route del 8.8.4.4/32 dev wg0; iptables -t mangle -D FORWARD -o wg0 -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu; iptables -t mangle -D FORWARD -i wg0 -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu; ip route flush cache
Table = off
MTU = 1280

[Peer]
PublicKey = SERVER_PUBLIC_KEY
AllowedIPs = 0.0.0.0/0
Endpoint = YOUR_VPN_SERVER_IP:PORT
PersistentKeepalive = 25

4. Enable Kernel IPv4 Forwarding

Enable packet forwarding in /etc/sysctl.conf:

sudo sysctl -w net.ipv4.ip_forward=1
echo "net.ipv4.ip_forward=1" | sudo tee -a /etc/sysctl.conf

5. DNS Configuration for DHCP Clients

Configure NetworkManager's shared dnsmasq instance to supply public DNS servers to hotspot clients:

sudo mkdir -p /etc/NetworkManager/dnsmasq-shared.d/
echo "dhcp-option=option:dns-server,8.8.8.8,8.8.4.4" | sudo tee /etc/NetworkManager/dnsmasq-shared.d/dns.conf

6. Monitoring and Verification

Check active DHCP leases granted to Wi-Fi clients:

cat /var/lib/NetworkManager/dnsmasq-wlan0.leases

Verify dnsmasq runtime process parameters:

ps aux | grep dnsmasq

How to Set Default Route and Network Metrics on Debian 12 (Bookworm) Using NetworkManager

On Debian 12 (Bookworm) and Raspberry Pi OS Bookworm, dhcpcd has been deprecated and replaced by NetworkManager as the default network management stack. Consequently, /etc/dhcpcd.conf is no longer present.

When multiple network interfaces (such as Ethernet eth0 and Wi-Fi wlan0) are connected simultaneously, the Linux kernel determines the default gateway based on routing metrics. Lower metric values take precedence over higher values.

Rule: Lower route metric = higher routing priority. To prioritize an interface for default internet access, assign it a lower metric than competing interfaces.

1. Inspect Current Routing Metrics

Check the existing routing table and metric values:

ip route show
# or:
route -n

2. List NetworkManager Connection Profiles

Identify the exact connection name you wish to adjust:

nmcli connection show

3. Adjust the Route Metric

You can set the route metric directly using a single nmcli command:

# Set metric to 100 for higher priority (e.g. Ethernet)
nmcli connection modify "Wired connection 1" ipv4.route-metric 100

# Reactivate the connection to apply changes
nmcli connection up "Wired connection 1"

Alternatively, you can edit the connection interactively:

nmcli connection edit "Wired connection 1"
nmcli> set ipv4.route-metric 100
nmcli> save
nmcli> quit

Run ip route show again to verify that your preferred connection now holds the lowest metric on the default route.