Time Synchronization Services test warning "Configuration is not working normally".

Products

• VMware vSphere ESXi

Issue/Introduction

Time Synchronization Services test warning "Configuration is not working normally" after configuring NTP on an ESXI 8.x

The test result in the following text area will show a message like the following example:

Service analysis started on host: ExampleHost
Test started at: 2024-06-28T14:00:02Z
Time Service is administratively enabled.
Verifying NTP service.
NTP server: ExampleIPAdress resolves IPv4: ExampleIPAddress
Virtual NIC vmkX : Admin: Up
IP Interface: vmkX IPv4 Address: STATIC ExampleIPAdress
IP Interface: vmkX connected to 1XX on distributed vswitch
IP Network Stack: defaultTcpipStack
Firewall Rule: ntpClient allows traffic on port: 123
Firewall Rule: ntpClient allows all IPs
ntpd is running, PID: 2XXXXX
Kernel clock type: ntp
NTP is not synced
NTP never was synchronized.
Service analysis completed.

Environment

ESXI 8.x

ntp-4.2.8p17

Cause

This is a known NTP issue with ntp-4.2.8p17 described in detail here: https://bugs.ntp.org/show_bug.cgi?id=3877

Per the linked report, this change rejects certain NTP packets that are considered poorly formed or invalid.

This is done to ensure that the NTP daemon consumes NTP network packets securely.

Resolution

This will be addressed in a future release of ESXI 8.x.

Additional Information

To troubleshoot this issue, run the following commands on the affected ESXI hosts:

traceroute <NTPserverIP>

tcpdump-uw -c 10 port 123 -w traffic.pcap