Internet Connection Sharing: Difference between revisions

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VisualWikitext

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 === Configuration ===
-Persistent share an existing internet connection of a wired interface <code>eth0</code> using a wifi hotspot on <code>wlan0</code> with the access point name <code>My Wifi Hotspot</code>. The network is protected with a simple WPA2 pre-shared key <code>12345678</code>.
+Persistently share an existing internet connection of a wired interface <code>eth0</code> using a wifi hotspot on <code>wlan0</code> with the access point name <code>My Wifi Hotspot</code>. The network is protected with a simple WPA2 pre-shared key <code>12345678</code>.
 <syntaxhighlight lang="nix">
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 # Get handle_number with: nft -a list table nat
 nft delete rule nat POSTROUTING handle <handle_number>
+</syntaxhighlight>
+=== Configuration ===
+Persistently share an existing internet connection on interface `wlan0` to clients connected on an ethernet interface `eth0`. Tested where `wlan0` is a wireless interface, but it should work with a different ethernet interface as well. You do not need to manually open port 53.
+<syntaxhighlight lang="nix">
+# Set a static IP on the "downstream" interface
+networking.interfaces."eth0" = {
+  useDHCP = false;
+  ipv4.addresses = [{
+    address = "10.0.0.1";
+    prefixLength = 24;
+  }];
+};
+networking.firewall.extraCommands = ''
+  # Set up SNAT on packets going from downstream to the wider internet
+  iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE
+  # Accept all connections from downstream. May not be necessary
+  iptables -A INPUT -i enp2s0 -j ACCEPT
+'';
+# Run a DHCP server on the downstream interface
+services.kea.dhcp4 = {
+  enable = true;
+  settings = {
+    interfaces-config = {
+      interfaces = [
+        "eth0"
+      ];
+    };
+    lease-database = {
+      name = "/var/lib/kea/dhcp4.leases";
+      persist = true;
+      type = "memfile";
+    };
+    rebind-timer = 2000;
+    renew-timer = 1000;
+    subnet4 = [
+      {
+        id = 1;
+        pools = [
+          {
+            pool = "10.0.0.2 - 10.0.0.255";
+          }
+        ];
+        subnet = "10.0.0.1/24";
+      }
+    ];
+    valid-lifetime = 4000;
+    option-data = [{
+      name = "routers";
+      data = "10.0.0.1";
+    }];
+  };
+};
 </syntaxhighlight>
 [[Category:Networking]]