Hello.

lib/default.nix

@@ -51,7 +51,9 @@
     ];
     autoStart  = true;
     privateNetwork = true;
-    hostBridge = "br0";
+    # hostBridge = "br0";
+    hostAddress = "192.168.2.1";
+    localAddress = "192.168.2.2/24";
     restartIfChanged = true;
     enableTun = true;
     additionalCapabilities = [ "CAP_NET_ADMIN" "CAP_NET_RAW" ];

nixos/containers/default.nix

@@ -24,6 +24,6 @@
   boot.isContainer = true;
   services.tailscale.authKeyFile = "/run/secrets/tailscale_key";
   networking.hostName = "${hostname}";
-  networking.interfaces."eth0".useDHCP = true;
+  # networking.interfaces."eth0".useDHCP = true;
   system.stateVersion = stateVersion;
 }

nixos/hosts/framework-server/containers.nix

@@ -1,22 +1,20 @@
-{ lib, self, inputs, outputs, stateVersion, hmStateVersion, ... }:
+{ config, lib, self, inputs, outputs, stateVersion, hmStateVersion, ... }:
 let 
   libx = import ../../../lib { inherit lib self inputs outputs stateVersion hmStateVersion; };
+  lanInterface = "enp0s13f0u4";
 in {
   containers = {
     rdesktop = libx.mkContainer { hostname = "rdesktop"; };
   };
 
+  networking.firewall.extraCommands = ''
+    iptables -w -t nat -A nixos-nat-post -s ${config.containers.rdesktop.localAddress} -j MASQUERADE
+  '';
 
-  networking = {
-    bridges.br0.interfaces = [ "enp0s13f0u4" ];
-    interfaces.br0.ipv4.addresses = [{ address = "192.168.2.1"; prefixLength = 24; }];
+  networking.nat = {
+    enable = true;
+    internalInterfaces = [ "ve-rdesktop" ];
+    externalInterface  = lanInterface;
+    extraCommands = "iptables -t nat -A POSTROUTING -o ${lanInterface} -j MASQUERADE";
   };
-
-#  networking.nat = {
-#    enable = true;
-#    internalInterfaces = [ 
-#      "ve-rdesktop" 
-#    ];
-#    externalInterface = "enp0s13f0u4";
-#  };
 }