Pick random IP address to avoid conflict with WAN

[chGoodchild]

To achieve what you're describing, you'll need to modify your router's configuration. This typically involves editing the DHCP server settings and possibly the network interface configuration. Here's a general approach to accomplish this:

1. Create a script to generate a random IP address:

   First, you'll need a script that generates a random IP address of the form x.x.x.1. Here's a simple bash script that does this:

   #!/bin/sh
   echo $((RANDOM%254+1)).$((RANDOM%254+1)).$((RANDOM%254+1)).1

   Save this script as /usr/bin/random_ip.sh and make it executable:

   chmod +x /usr/bin/random_ip.sh

2. Modify the network configuration:

   You'll need to edit the network configuration file, which is typically located at /etc/config/network. Modify the LAN interface section to use the random IP:

   config interface 'lan'
       option type 'bridge'
       option ifname 'eth0.1'
       option proto 'static'
       option ipaddr '`/usr/bin/random_ip.sh`'
       option netmask '255.255.255.0'

3. Update DHCP server configuration:

   Edit the DHCP server configuration file, usually located at /etc/config/dhcp. Modify the LAN section to use the new random IP range:

   config dhcp 'lan'
       option interface 'lan'
       option start '100'
       option limit '150'
       option leasetime '12h'
       option dhcpv6 'server'
       option ra 'server'

4. Create a boot script:

   To ensure this happens at every boot, create a boot script:

   #!/bin/sh /etc/rc.common
   
   START=99
   
   start() {
      NEW_IP=$(/usr/bin/random_ip.sh)
      uci set network.lan.ipaddr="$NEW_IP"
      uci commit network
      /etc/init.d/network restart
      /etc/init.d/dnsmasq restart
   }

   Save this as /etc/init.d/random_lan_ip and make it executable:

   chmod +x /etc/init.d/random_lan_ip

   Enable it to run at boot:

   /etc/init.d/random_lan_ip enable

5. Reboot your router:

   After making these changes, reboot your router for the changes to take effect.

Please note:

• This solution assumes you're using OpenWrt or a similar Linux-based router firmware. The exact file locations and commands may vary depending on your specific router and firmware.
• Changing your LAN IP randomly may cause issues with devices that expect a consistent IP address for the router. You may need to adjust your network settings accordingly.
• Ensure that the random IP range doesn't conflict with common private IP ranges (like 192.168.x.x or 10.x.x.x) used by many upstream networks to minimize the chance of conflicts.

Always back up your current configuration before making these changes, and be prepared to reset your router if something goes wrong.