If no VR is specified, VR-Default will be chosen by default.
Please note that NTP feature support was added to EXOS in 12.7. From EXOS 12.7 until 15.4 the NTP XMOD was required in order to configure and use the feature. In EXOS 15.5 NTP was included in the standard EXOS image. No XMOD is required for EXOS versions 15.5 and up.