Add gre tunnel for hamnet

machines/warwick.nix

@@ -5,6 +5,32 @@
 
     nixosModule = {
       lab.monitoring.server.enable = true;
+
+      systemd.network = {
+        netdevs.hamgre = {
+          netdevConfig = {
+            Name = "hamgre";
+            Kind = "gre";
+            MTUBytes = "1468";
+          };
+
+          tunnelConfig = {
+            Remote = "145.220.78.4";
+            #Local = "192.145.57.90";
+          };
+        };
+
+        networks = {
+          "30-main-nic".networkConfig.Tunnel = "hamgre";
+          "40-hamgre" = {
+            matchConfig.Name = "hamgre";
+
+            networkConfig = {
+              Address = "44.137.61.34/30";
+            };
+          };
+        };
+      };
     };
   };
 }