// mapped interface isn't present, fallback to use the scope ID (which has no validation against
    // present interfaces)
    NetworkInterface scopedInterface = ip.getScopedInterface();
    if (scopedInterface != null) {
      return "%" + scopedInterface.getName();
    }
    int scope = ip.getScopeId();
    if (scope != 0) {
      return "%" + scope;
    }
    return "";