Setting NTP fails with the error 'NTP_SERVER_NAME is unreachable'

Products

• VMware vCenter Server 7.0
• VMware vCenter Server 8.0
• VMware Cloud Foundation 5.x
• VMware Cloud Foundation 4.x

Issue/Introduction

When NTP server setting on VAMI "TIME" -> "Time synchronization", it fails with the error 'NTP_SERVER_NAME is unreachable'.

If the Configure NTP workflow is being pushed from SDDC Manager, you may see below error in operationsmanager.log- "Error occurred while testing NTP servers on <VC-FQDN>"

 

Environment

vCenter 7.0/8.0

VMware Cloud Foundation 4.x/5.x

Cause

This issue happens if the connectivity between vCenter server and NTP server is not working.

Resolution

Use another NTP server which is reachable 

OR

Please contact your NTP/Network team to check the connectivity between VC and NTP server(s).

Additional Information

Additionally, a tcpdump capture may be useful in checking this as below- 

---
root@vc [ ~ ]# tcpdump -tttt -n port 123 and udp
:
YYYY-MM-DD TT:MM:SS.736368 IP y.y.y.y.56693 > x.x.x.x.123: NTPv4, Client, length 48   <--- Request to NTP server IP x.x.x.x
:                                                                                     <--- No response from NTP server
^C
1 packet captured
1 packet received by filter
0 packets dropped by kernel
root@vc [ ~ ]#
---