KB44457 - Frequent VIP flap is observed on Virtual Machines running on VMWare/ESXi in A/P cluster.

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Last Modified Date	4/30/2020 7:42 AM

Synopsis

This article describes a scenario where frequent VIP flap is observed on Virtual Machines running on VMWare/ESXi in A/P cluster.

Problem or Goal

Network Time Protocol (NTP) is a protocol used to synchronize system clock times in a network. This is very important for network devices to function correctly.

It is observed that Virtual Appliances deployed in A/P Cluster, frequently face VIP flaps when NTP Server is configured.

This issue applies to :

PCS/PPS Virtual Appliances running on VMWare/ESXi.
PCS/PPS Software versions 9.1R5 and below,

This issue doesn’t apply to :

Any PCS/PPS Physical (Hardware) Appliances.
Any other Non-VMWare/ESXi Virtual deployments.

Cause

This is due to a time deviation contributed by the bug in the PCS/PPS Virtual Appliance System Clock and is not related to the NTP Server.

If this issue is hit, you will see the following log entries in the PCS/PPS Event Logs (System -> Log/Monitoring -> Admin -> Log) similar to the ones specified below,

info - Default Network::System()[][] - 2020/02/26 10:55:26 - VPN - Time adjusted by 73.81355 seconds.
info - Default Network::System()[][] - 2020/02/26 11:56:30 - VPN - Time adjusted by 73.81654 seconds.
info - Default Network::System()[][] - 2020/02/26 12:57:34 - VPN - Time adjusted by 73.80965 seconds.
info - Default Network::System()[][] - 2020/02/26 14:08:38 - VPN - Time adjusted by 73.81568 seconds. 
info - Default Network::System()[][] - 2020/02/26 15:09:42 - VPN - Time adjusted by 73.82095 seconds.

Solution

The NTP feature has been refined from PCS/PPS 9.1R8, however, we have run into a couple of other issues as outlined in NTP issues post 9.1R8 upgrade on PCS/PPS Virtual Machines

Workaround:

1. Please enable "Synchronize guest time with host" under the Virtual Machine properties as show in the image below.

User-added image

2.   And, then discontinue using NTP Server for the time being,

i. Login to PCS/PPS device & Navigate to System -> Status -> Overview.
ii.   Click on Edit next to “System Date & Time”
iii.   Select Set Time Manually Radio Button & Save changes.
iv.   This will help sync the Virtual Machine with the Hypervisor going further.

Note:

•   All the cluster nodes (Same ESXi or otherwise), license servers, authentication servers etc., should not have any time deviations. Else, this can cause issues.
•   The Virtual appliance should have only one source of Time Sync (Hypervisor or NTP Server, NOT both). This can otherwise result is an unexpected behaviour.
•   Once the issue is resolved, we strictly recommend to revert to NTP Server settings.

Related Articles

KB44457 - Frequent VIP flap is observed on Virtual Machines running on VMWare/ESXi in A/P cluster.

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