Unable to view one of the vCenter Server Instances in an Enhanced Linked Mode deployment for a SDDC Manager setup
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Unable to view one of the vCenter Server Instances in an Enhanced Linked Mode deployment for a SDDC Manager setup

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Article ID: 339526

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Updated On:

Products

VMware Cloud Foundation

Issue/Introduction

If you have two or more vCenter Servers in Enhanced Linked Mode. you cannot view one of the vCenter Server instances in the inventory.

Environment

VMware Cloud Foundation 2.0.x
VMware Cloud Foundation 2.1.x

Cause

This issue occurs due various reasons, but one of the main reason is the time differences between the PSC's and the vCenter Server Instances.

Resolution

All components in VCF (Vmware Cloud Foundation) sync their time with SDDC manager VM, i.e. the VRM VM. VRM VM acts as the source NTP server for the PSCs and the vCenter Servers.

Due to any issue if the communication between the VRM VM and VC/PSC breaks for a prolonged time period, there are chances that the PSC/VC instances can experience time-skew issue.

To verify that you are hitting this issue, SSH into your VRM/PSC/VC instances and run the date command.

It will give you the current date and time on the node. If the time is not correct and not in sync with the source NTP server, run ntpq -p on the node
You see output similar to:

remote         refid      st   t   when   poll   reach   delay  offset jitter
=============================================================================

*10.11.12.130  1.0.0.0     1   u    46     64     377     43.76  5.58   40000

 

The field returned by ntpq have these meanings:

remote

Hostname or IP address of the configured upstream NTP server.

refid

Identification of the time stream to which the NTP server is synchronized.

st

Stratum is a value representing the hierarchy of the upstream NTP servers. Higher values indicate NTP servers further away from the root time source. Values are relative, and can be set manually by an NTP server.

t

Type of packet exchange used for NTP communication. Usually "u" for unicast UDP.

when

Quantity of seconds which have elapsed since the last attempted poll of the configured upstream NTP server.

poll

Interval in seconds which the client node polls the configured NTP server.

reach

An 8-bit shift register in octal (base 8), with each bit representing success (1) or failure (0) in contacting the configured NTP server. A value of 377 is 11111111 (base 2), which indicates that every query was successful during the last 8 poll intervals.

delay

Round trip delay (in milliseconds) for communication between the configured NTP server and the client

offset

The offset (in milliseconds) between the time on the configured NTP server and the client. A value closer to 0 is ideal.

jitter

The observed timing jitter or variation between clock pulses of time with the configured NTP server. A value closer to 0 is ideal.

 

Under remote, you should see the IP or the FQDN of the VRM machine until changed.

If the offset and jitter is any number other than 0, restart the NTP service on the node so that the client syncs again with the NTP server.

To restart ntp service, run these commnads:

Service ntp stop
Service ntp start

This should force ntp to resync time for your node. To verify that offset and jitter have been set to 0 again.

Run the ntpq -p command again and check the values.

Once the time on all nodes are in sync, try logging in to one of the vCenter Server again. You should now see all vCenter Server instances participating in Enhanced Linked Mode.