we should NOT set a gateway

replace router dns image

Update docs/routers/OPNsense.md

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add opnsense

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replace IP with MAC

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Update docs/routers/OPNsense.md

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docs/routers/OPNsense.md

@@ -0,0 +1,103 @@
+This guide was developed using a OPNsense 25.1.1. Following the first method below will have you adding your Pi-hole as a DNS server for all devices on your LAN. Following the second method below will have DNS queries route through your OPNsense and then to your Pi-hole. Either option is valid, depending on your specific requirements, but it is recommended to choose one or the other - not both.
+
+Optionally, there is also the possibility to block DNS traffic to other, non-Pi-hole DNS servers via firewall rules. This can be used to prevent clients like Chromecasts of using their hardcoded DNS servers.
+
+Beware: This tutorial does not explain on how to block DoH or DoT.
+
+### Grab your IPv4 and IPv6 address from your Pi-hole
+
+SSH into your Pi-hole. A quick `ifconfig eth0` (substituting `eth0` for the applicable network interface) will get you the address information:
+
+```
+eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
+        inet 10.0.51.2  netmask 255.255.255.0  broadcast 192.168.0.255
+        inet6 2001:470:5:3::8ed  prefixlen 128  scopeid 0x0<global>
+        inet6 2001:470:5:3:8d70:e92e:7030:6eef  prefixlen 64  scopeid 0x0<global>
+        inet6 fe80::337f:710d:6781:4c85  prefixlen 64  scopeid 0x20<link>
+        ether dc:a6:32:0e:31:2d  txqueuelen 1000  (Ethernet)
+        RX packets 1297459  bytes 1279521260 (1.1 GiB)
+        RX errors 0  dropped 0  overruns 0  frame 0
+        TX packets 2315988  bytes 2766370095 (2.5 GiB)
+        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
+```
+
+Take note of the `inet` address, and the `inet6` address which starts with `fe` (denotes a local link or LAN address). Those are the IPs which you'll use as your DNS servers. For this example, we'll be using the `10.0.51.2` and `fe80::337f:710d:6781:4c85` IPs for the following directions.
+
+### Method 1: Distribute Pi-hole as DNS server via DHCP
+
+Choosing this option will have DNS queries taking the following path:
+
+```
+(Clients) -> Pi-hole -> Upstream DNS Server
+```
+
+#### IPv4
+
+Go to **Services** --> **ISC DHCPv4** and click on the interface that you want to modify.
+Under **DNS servers** enter your Pi-hole IPv4 address into the first line.
+Leave the second line blank unless you have another Pi-hole host running.
+
+![Screenshot of OPNsense DHCPv4 Settings](../images/routers/opnsense-dhcpv4.png)
+
+#### IPv6
+
+
+Go to **Interfaces** and click on the interface that you want to modify.
+Under **Manual configuration** check "Allow manual adjustment of DHCPv6 and Router Advertisements"
+
+![Screenshot of OPNsense IPv6 manual RA Settings](../images/routers/opnsense-ipv6-manual-ra.png)
+
+Now go to **Services** --> **Router Advertisement** and click on the interface that you want to modify.
+Under **DNS servers** enter your Pi-Holes IPv6 address into the first line.
+Leave the second line blank unless you have another Pi-hole host running.
+
+![Screenshot of OPNsense IPv6 RA Settings](../images/routers/opensense-ra.png)
+
+Beware: Link local IPv6 are not reachable from other VLANs.
+
+
+All client devices on your network should now automatically be configured with a single IPv4 and single IPv6 address for DNS resolution. If you don't see your client devices update quickly enough, you *can* toggle Wi-Fi off/on or disconnect the Ethernet cable for a couple of seconds and then reconnect it.
+
+### Method 2: Using your Pi-hole as DNS server for your OPNsense
+
+If you'd rather have your OPNsense forward all DNS traffic to Pi-hole, you can complete this *alternative* step.
+Doing so will have DNS queries taking the following path:
+
+```
+(Clients) -> OPNsense -> Pi-hole -> Upstream DNS Server
+```
+
+!!! warning
+    Keep in mind that if you are using your OPNsense IP address as an upstream resolver for your Pi-hole together with this configuration, ***this will cause a resolver loop***. Make sure to have another upstream DNS server(s) set in your Pi-hole's configuration, or use Pi-hole as [your own recursive DNS server with Unbound](https://docs.pi-hole.net/guides/dns/unbound/?h=unbound#configure-unbound).
+
+1. In Pi-hole, navigate to `Settings -> DNS` and ensure you have at least one external upstream DNS server enabled.
+2. In OPNsense navigate to `Settings -> General -> Networking`.
+3. Under DNS Servers, enter the IPv4 and or IPv6 address of your Pi-hole host.
+4. Uncheck `Allow DNS server list to the overridden by DHCP/PPP on WAN`.
+5. Click Save.
+
+![Screenshot of OPNsense DNS WAN Settings](../images/routers/opnsense-dns-wan.png)
+
+### Block other DNS servers (optional)
+
+Some clients have hardcoded DNS settings. To prevent them from circumventing our Pi-Hole, we can optionally block all DNS request that are not coming from our Pi-Hole.
+!!! warning
+    If your device does not have any fallback from the hardcoded DNS settings, this could break its DNS.
+
+We first create an Alias for Pi-holes MAC address.
+Go to **Firewall** --> **Aliases** scroll down and click on the plus button to create a new alias.
+Give it a Name, select the type MAC address and enter the MAC address from Pi-Hole into the "Content" field and then click save.
+The MAC address of your device you can find out by looking at the line `ether` from our `ifconfig eth0` output we got earlier.
+
+![Screenshot of OPNsense Aliases](../images/routers/opnsense-alias.png)
+
+Now go to **Firewall** --> **Rules** and click on the interface that you want to modify.
+
+We create one rule to allow Pi-hole to do DNS.
+After that rule, we create a rule to reject ALL DNS. It is important that this reject rule is after the other rule.
+OPNsense does the first rule that matches, if we have our reject rule first, Pi-hole can not reach any DNS servers.
+It should look something like this:
+
+![Screenshot of OPNsense Firewall rules](../images/routers/opnsense-firewall-rule.png)
+
+We don't need a rule to allow for example device 10.0.51.10 to reach our Pi-hole at 10.0.51.2, since they are both on the same network, DNS request will not be routed through OPNsense. Instead the client 10.0.51.10 will directly contact Pi-hole for DNS requests.

mkdocs.yml

@@ -214,6 +214,7 @@ nav:
     - 'Fritz!Box (EN)': routers/fritzbox.md
     - 'Fritz!Box (DE)': routers/fritzbox-de.md
     - 'Nokia G-240W-B': routers/nokia-G240WB.md
+    - 'OPNsense': routers/OPNsense.md
     - 'TP-Link': routers/tp-link.md
     - 'Ubiquiti USG': routers/ubiquiti-usg.md
   - 'FAQ': main/faq.md