nixbld: add backup internet connection

nixbld-etc-nixos/configuration.nix

@@ -6,6 +6,7 @@
 
 let
   netifWan = "enp4s0";
+  netifWanBackup = "enp11s0";
   netifLan = "enp5s0f1";
   netifWifi = "wlp6s0";
   netifSit = "henet0";
@@ -94,7 +95,22 @@ in
       allowedUDPPorts = [ 53 67 500 4500 ];
       trustedInterfaces = [ netifLan ];
     };
-    interfaces."${netifWan}".useDHCP = true;
+    useDHCP = false;
+    interfaces."${netifWan}".useDHCP = true;  # PCCW - always wants active DHCP lease or cuts you off
+    interfaces."${netifWanBackup}" = {        # HKBN - no DHCP with static IP service
+      ipv4.addresses = [{
+        address = "202.77.7.238";
+        prefixLength = 30;
+      }];
+      ipv4.routes = [
+        {
+          address = "0.0.0.0";
+          prefixLength = 0;
+          via = "202.77.7.237";
+          options.table = "2";
+        }
+      ];
+    };
     interfaces."${netifLan}" = {
       ipv4.addresses = [{
         address = "192.168.1.1";
@@ -112,6 +128,11 @@ in
           prefixLength = 24;
           options.table = "1";
         }
+        {
+          address = "192.168.1.0";
+          prefixLength = 24;
+          options.table = "2";
+        }
       ];
     };
     interfaces."${netifWifi}" = {
@@ -243,7 +264,16 @@ in
     };
   };
 
-  systemd.services.custom-network-setup = {
+  systemd.services.network-custom-route-backup = {
+    wantedBy = [ "network.target" ];
+    serviceConfig = {
+      Type = "oneshot";
+      RemainAfterExit = true;
+      ExecStart = "${pkgs.iproute2}/bin/ip rule add from 202.77.7.238/30 table 2";
+      ExecStop = "${pkgs.iproute2}/bin/ip rule del table 2";
+    };
+  };
+  systemd.services.network-custom-route-alt = {
     wantedBy = [ "network.target" ];
     serviceConfig = {
       Type = "oneshot";