diff --git a/modules/clan/phonebox/default.nix b/modules/clan/phonebox/default.nix
index 80f0c92..0e48c16 100644
--- a/modules/clan/phonebox/default.nix
+++ b/modules/clan/phonebox/default.nix
@@ -6,10 +6,18 @@
   manifest.categories = [ "System" ];
 
   roles.default = {
+    interface =
+      { lib, ... }:
+      {
+        options.ata-ethernet-iface = lib.mkOption {
+          type = lib.types.str;
+          description = "An Ethernet interface that connect to ATA box.";
+        };
+      };
     perInstance =
       {
-        instanceName,
         roles,
+        settings,
       }:
       {
         nixosModule =
@@ -20,9 +28,9 @@
           }:
           let
             user = "asterisk";
-            ata-interface = "";
             rtpPortFrom = 10000;
             rtpPortTo = 20000;
+            ata-interface = settings.ata-ethernet-iface;
 
             genServerSIPEndpoint =
               { hostname, address }: