Sending All DNS Traffic on LAN via PiHole

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Ok, understoood.
Your existing setup just blocks unsolicited DNS queries to external DNS, but you want to redirect it to be processed through your Pi-hole instead.

Let me rephrase my cautious recommendation to go without eth1 into something more action-oriented :wink:
Assuming that you have gigabit eth0 and otherwise kept your setup from Pihole plus Guest Wifi on different IP range, try the following eth1-free configuration:

  • unplug your second ethernet dongle (eth1)
  • undo any eth1 related configurations, including any iptables NAT entries
  • make sure that your eth0 interface is still configured to use your localhost DNS and your router by checking these lines in /etc/dhcpcd.conf
   static ip_address=192.168.1.2/24
   static routers=192.168.1.1
   static domain_name_servers=127.0.0.1
  • configure Pi-holes Settings|DHCP to hand out itself (192.168.1.2) as router (don't forget to save)
  • configure iptables to redirect incoming eth0 UDP/TCP traffic with a DNS target port to be handled by your machine's DNS:
   iptables -t nat -A PREROUTING -i eth0 -p udp --dport 53 -j REDIRECT --to-port 53
   iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 53 -j REDIRECT --to-port 53
  • (optional should you consider extending this to your 10.0.0.x guest wlan, also add the following)
   iptables -t nat -A PREROUTING -i wlan0 -p udp --dport 53 -j REDIRECT
   iptables -t nat -A PREROUTING -i wlan0 -p tcp --dport 53 -j REDIRECT

Bottom line difference to your solution:
You don't need a second ethernet dongle - save some power :wink: