Exclusive Fix: VMware vCenter Upgrade Failed 6.7 to 7.0 to 8.0 to 9.0

It is very common to get many errors when try to upgrade VMware vCenter from 6.7 to 7.0 and 7.0 to 8.0 to 9.0.

I also struggled with same VMware vCenter upgrade errors and after many hours of investigation of error logs and step to step troubleshooting, finally found the possible resolutions to fix such issues / errors.

Upgrading VMware vCenter Server from version 7 to 8 to 9 is a major infrastructure change that many organisations plan to adopt for improved security, performance, and modern management capabilities. However, despite careful preparation, administrators often face unexpected upgrade failures during this process. These failures can occur at different stages, such as pre-checks, deployment, data migration, or service startup after the upgrade.

Common issues include DNS and hostname misconfiguration, unsupported ESXi versions, certificate expiration, plugin incompatibility, or insufficient system resources. When not addressed properly, an upgrade failure can lead to extended downtime and operational risk for production environments.

This guide focuses on practical troubleshooting steps for resolving VMware vCenter 7 to 8 to 9 upgrade failures. It explains the most common causes, how to identify them using logs and validation checks, and the safest recovery methods to restore services quickly. The goal is to help administrators complete the upgrade successfully while minimising risk and downtime.

While trying to upgrade VMware vCenter version 6.7 to 7.x or 7.x to 8.x to 9.0 may counter many issues / errors as mentioned below:

vCenter Upgrade known issues / Errors

List of issues / errors while upgrading VMware vCenter version 6.7 to 7.0 or 7.0 to 8.0 to 9.0.

• Pre-upgrade check failed due the following problem: Error in method invocation [Error 1] Unknown host
• Error in method invocation [Error 1] Unknown host
• Error during vCenter upgrade stage 2 pre-check failed
• Error in method invocation to source vCenter stage 2
• New vCenter can not communicate to Source vCenter via ESXi
• Error vCenter upgrade failed VCSA 6.7 to 7.0 (unknown host)
• Error vCenter upgrade failed VCSA 7.0 to 8.0 (unknown host)

If you are facing any issue from above list of issues, then you are at right place to get resolution.

All possible solutions are mentioned below to fix above such issues.

Possible Resolutions of vCenter upgrade failures

Let’s explore each resolution of above issues and errors encounters during vCenter upgrade from version 6.7 to 7.0 and 7.0 8.0.

Solution 1: NTP sync & correct Timezone

It is always recommended that all VMware ESXi hosts and vCenter appliance time and time zone must be in sync with same/common NTP servers.

Validate ESXi time & NTP server

Refer link: Configuring NTP on an ESXi host

Validate vCenter time & NTP server

Refer KB link: Configuring NTP on vCenter Server

Solution 2: Turn on SSH Service

SSH service is required to enable communication and system data transfer between vCenter and ESXi hosts

• Refer link: How to enable SSH on VMware vCenter
• Refer link How to enable SSH on VMware ESXi host

Solution 3: DNS Lookup for Forward & Reverse zone

It’s very common that VMware administrator does not request AD/DNS team to create A (Forward) and PTR ( Reverse ) records in DNS for nslookup for ESXi hosts and vCenter.

Later, it starts creating issues and pop-up errors, to avoid any such issues, always create DNS entry.

Refer Link: How to create DNS A & PTR records

Run following command to check DNS resolution:

$nslookup <Enter ESXi Host IP or Hostname>

Example:
$nslookup 192.168.100.10
OR
$nslookup myesxihost01

Solution 4: Use vCenter & ESXi FQDN Instead IP address

It most important and common issue, VMware administrator does not notice. Always use same ESXi and vCenter IP address, hostname and FQDN as it is showing / mapped on vCenter inventory.

Important Tips

Tip 1: If ESXi hosts are mapped on vCenter’s inventory with IP addresses then use IP address only while upgrading vCenter and fill-up same information during vCenter upgrade wizard.

Tip 2: If ESXi hosts are mapped on vCenter’s inventory with hostname or FQDN then use as-is, while upgrading vCenter and fill-up same information during vCenter upgrade wizard

Example: See in above screenshot -all hosts are mapped with hostname/FQDN in vCenter’s inventory. Therefore, use same information as-is during vCenter upgrade wizard.

Solution 5: Ensure ping readability among ESXi hosts & vCenter

It’s important to check connectivity and reachability among ESXi hosts and vCenter.

Step 1: Login to ESXi and run following command to check reachability over network

$ ping <<Enter vCenter IP or Hostname>

Example: ping 192.168.100.100

Step 2: Login to vCenter and run following command to check reachability over network

$ ping <Enter ESXi Host IP or Hostname>

Example:
$ping 192.168.100.10

Solution 6: Ensure port no. 22, 80, 902, 443 & 5480 are open for ESXi & vCenter

Ensure that VMware ESXi and vCenter mandate ports are open on ESXi firewall and gateway network firewall.

Refer link: ESXi & vCenter network ports details

Solution 7: Change DRS cluster settings

Ideally, both VMware vCenters ( current vCenter and newly deploying vCenter ) should be on same ESXi host during upgradation process, otherwise upgrade process will be failed with errors.

If DRS is enabled with full-automatic VM migration mode then vCenter VMs may live-migrate on different ESXi hosts then vCenter upgradation process will be stuck and failed.

Note: Set DRS > Automation > Automation level > Manual

Solution 8: Upgrade Distributed switch version to least 7.x or 8.x

Distributed switch version should be upgraded as per vCenter version or N-1 only not below that.

If You are going to upgrade from vCenter 7.0 to 8.0 then Distributed switch version must be least 7.0 or later.

Refer link: How to upgrade vCenter Distributed Switch Version

Solution 9: Patch vCenter with latest / higher build number

Last but not the least, before any major upgrade, always patch vCenter to higher patch built to avoid any existing bug in current patch version.

Example: if you’re running vCenter 7.0 U3O (22357613) then patch with latest higher version 7.0U3T (24322018) to avoid any know issue on old patch.

Refer link: Check vCenter patch releases

Hopefully, this blog helped you to resolve vCenter upgrade issues.

Frequently Ask Questions (FAQs)

Conclusion: VMware vCenter 7 to 8 to 9 Upgrade Troubleshooting

Upgrading VMware vCenter from version 7 to 8 is a critical task that requires careful planning and validation. Most upgrade failures occur due to common but often overlooked issues such as DNS misconfiguration, unsupported ESXi versions, insufficient system resources, certificate problems, or incompatible plugins. Addressing these prerequisites in advance significantly reduces the risk of upgrade failure.

When an upgrade does fail, reviewing installer logs, validating pre-check requirements, and reverting to a clean snapshot remain the safest and most effective recovery options. Administrators should never attempt repeated upgrades without identifying and resolving the root cause, as this can lead to service instability and extended downtime.

By following VMware best practices, performing thorough pre-upgrade checks, and maintaining proper backups, organisations can ensure a smooth and successful transition to vCenter 8. A structured troubleshooting approach not only saves time but also helps maintain stability across the virtual infrastructure.

Manish Kumar

I’m Manish Kumar, founder of HyperHCI.com and a senior IT consultant with 13+ years of experience in infrastructure design and cybersecurity. An official certified SME for ISC2 and Nutanix, Also, certified in CISSP, CompTIA Security+, VMware and AWS. My expertise covers HCI, virtualization, cloud computing, network and security across Nutanix, VMware, and AWS platforms Read more