无VPN实现两个隔离系统间路由：树莓派特殊组网场景求助

Alright, let's break down how to get traffic flowing between your two Raspberry Pi Wi-Fi APs without needing a VPN. Your existing wired cross-cable setup is perfect as the backbone for this routing—here's exactly what to do:

1. Confirm Wi-Fi AP Subnet Configurations #

First, make sure each Pi's Wi-Fi AP (wlan0) has a unique, non-overlapping subnet. For example:

• Device A: Set wlan0 to static IP 192.168.1.1/24, configure DHCP to assign addresses like 192.168.1.10–100
• Device B: Set wlan0 to static IP 192.168.2.1/24, configure DHCP to assign addresses like 192.168.2.10–100

(If you already have this set up, skip to the next step.)

2. Enable IP Forwarding on Both Pis #

Linux blocks IP packet forwarding by default—we need to enable it to let each Pi route traffic between its Wi-Fi and Ethernet interfaces:

• Temporary fix (resets on reboot):

  echo 1 > /proc/sys/net/ipv4/ip_forward
  

• Permanent fix:
  Edit /etc/sysctl.conf and uncomment the line:

  net.ipv4.ip_forward=1
  

  Then apply the change immediately:

  sysctl -p
  

3. Add Static Routes on Each Pi #

We need to tell each Pi where to send traffic destined for the other Pi's Wi-Fi subnet:

• On Device A: Route traffic for Device B's Wi-Fi subnet (192.168.2.0/24) through Device B's Ethernet IP (10.5.10.2)

  ip route add 192.168.2.0/24 via 10.5.10.2 dev eth0
  

  To make this permanent, add the following line to /etc/dhcpcd.conf (Raspbian uses dhcpcd for network config):

  static route 192.168.2.0/24 255.255.255.0 10.5.10.2
  

• On Device B: Route traffic for Device A's Wi-Fi subnet (192.168.1.0/24) through Device A's Ethernet IP (10.5.10.1)

  ip route add 192.168.1.0/24 via 10.5.10.1 dev eth0
  

  Permanent config in /etc/dhcpcd.conf:

  static route 192.168.1.0/24 255.255.255.0 10.5.10.1
  

4. Configure DHCP to Push Routes to Clients (Optional but Recommended) #

To avoid manually setting routes on every Wi-Fi client, configure your DHCP server (likely dnsmasq) to push the necessary routes:

• On Device A: Edit /etc/dnsmasq.conf and add:

  # Push default gateway (Device A's wlan0 IP)
  dhcp-option=3,192.168.1.1
  # Push route to Device B's Wi-Fi subnet
  dhcp-option=121,192.168.2.0/24,10.5.10.1
  

• On Device B: Edit /etc/dnsmasq.conf and add:

  dhcp-option=3,192.168.2.1
  dhcp-option=121,192.168.1.0/24,10.5.10.2
  

  Restart dnsmasq to apply changes:

  sudo systemctl restart dnsmasq
  

5. Allow Forwarding in IPTables (If Needed) #

If traffic still isn't flowing, check if iptables is blocking forwarding. Allow traffic between eth0 and wlan0 on both Pis:

iptables -A FORWARD -i eth0 -o wlan0 -j ACCEPT
iptables -A FORWARD -i wlan0 -o eth0 -j ACCEPT

To save these rules permanently, install iptables-persistent:

sudo apt-get install iptables-persistent

Follow the prompts to save your current rules—they'll load automatically on boot.

6. Verify Connectivity #

Test the setup by pinging a client on Device B's Wi-Fi from a client on Device A's Wi-Fi (and vice versa). If the ping goes through, you're good to go!

Content of the question comes from Stack Exchange, question author: Steven Sokol