For Citrix ADC VPX instances deployed on VMware ESXi hypervisor, the Citrix ADC system time might go out of sync and consequently network time protocol (NTP) synchronization is lost. This problem occurs due to an issue with VMware ACPI timer emulation.

tail -f ntpd.log
6 Dec 01:06:23 ntpd[42663]: Listen normally on 7 lo0 [fe80::1%5]:123
6 Dec 01:06:23 ntpd[42663]: Listening on routing socket on fd #28 for interface updates
6 Dec 01:06:23 ntpd[42663]: kernel reports TIME_ERROR: 0x4041: Clock Unsynchronized
6 Dec 01:06:23 ntpd[42663]: 0.0.0.0 c01d 0d kern kernel time sync enabled
6 Dec 01:06:23 ntpd[42663]: kernel reports TIME_ERROR: 0x4041: Clock Unsynchronized
6 Dec 01:06:23 ntpd[42663]: 0.0.0.0 c012 02 freq_set kernel 0.000 PPM
6 Dec 01:06:23 ntpd[42663]: 0.0.0.0 c011 01 freq_not_set
6 Dec 01:06:23 ntpd[42663]: 0.0.0.0 c016 06 restart
6 Dec 02:06:23 ntpd[42663]: frequency file /var/db/ntp.drift.TEMP: No such file or directory
 

Workaround:
Switch to a different timer emulation by following these steps:

1. Check the timer choices using the “sysctl kern.timecounter.choice” command.
2. If ACPI timer (ACPI-safe or ACPI-fast) is highest, select the next highest non-ACPI timer.
3. Assign the timer to sysctl kern.timecounter.hardware.

For example, if the highest non-acpi timer is i8254, run the following command at the ADC shell prompt:
"sysctl kern.timecounter.hardware=i8254".

To preserve the settings across reboots, add the preceding command to “/nsconfig/rc.netscaler” file.

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Problem Cause

ACPI emulation from VMware 7.0 onwards has some issues