{
  roles.default.perInstance = { settings, ... }: {
    nixosModule =
      {
        config,
        lib,
        ...
      }:
      let
      in
      {

        config = lib.mkIf (settings.proxy.enable) {
          assertions = [
            {
              assertion = lib.all (v: settings.vlans ? ${v}) settings.proxy.allowVlans;
              message = "cnx.router.proxy.allowVlans must name VLANs defined in cnx.router.vlans.";
            }
          ];

        };

      };
  };
}