I have N7k with NX-OS 6.2 , and divided with one admin vdc and other 3 vdc's.
I have external NTP server connected to non admin vdc "server VDC", I have configured NTP on admin and non admin VDCs, from admin VDC NTP it works fine but other vdcs not working, from other vdcs I can ping the NTP servers via loopback0 but when show ntp status I don't see anything and I tried to configure "clock protocol ntp vdc x" on the admin vdc but the same below the config:
ntp server 192.168.30.100 prefer use-vrf management ntp server 192.168.30.101 use-vrf management ntp source-interface mgmt0
NON admin VDC
ntp server 192.168.30.100 prefer ntp server 192.168.30.101 ntp source-interface loopback 0