"The source machine hostname 'IP/hostname' resolves to IPv6 address(es) 'ffff:###.##.##.##' communication error, but IPv6 networking will not be preserved after the upgrade" while upgrading VCSA 7.0/8.0 fails at precheck

Products

• VMware vCenter Server

Issue/Introduction

When upgrading a vCenter Server Appliance (VCSA) from 7.0 to 8.0, the upgrade process fails at Stage 2 → Pre-Checks due to an IPv6 resolution issue.

Symptoms:

• Upgrade is stuck at Stage 2 → Pre-Checks.
• vCenter is deployed using an IP address as PNID (Primary Network Identifier).
• IPv6 is disabled on vCenter.
• Error observed during Pre-Checks (Phase 2) when vCenter IP is ###.###.###.###.

 

"Error: 

The source machine hostname '###.##.##.##' resolves to IPv6 address(es) 'ffff:###.##.##.##', but IPv6 networking will not be preserved after the upgrade. This will prevent certain services preferring IPv6 from establishing network communication.

 

Resolution

Either remove the DNS IPv6 entry for hostname '###.###.###.###' or change the network configuration of the source machine to pure IPv6, or in case a dual networking stack is needed, set a static IPv6 address."

Environment

VMware vCenter Server Appliance 6.7.x

VMware vCenter Server Appliance 7.0.x

VMware vCenter Server Appliance 8.0.x

Cause

The upgrade scripts verify whether the source vCenter hostname/IP resolves to an IPv6 address.

• If IPv6 resolution exists but IPv6 networking is not enabled on the vCenter appliance, the upgrade precheck fails.
• This is to prevent post-upgrade communication failures for services that prefer IPv6.

 

Resolution

From the error message, the supported resolutions are:

• Option 1: Remove the DNS IPv6 entry for hostname IP/VC Name.
• Option 2: Change the network configuration of the source machine to pure IPv6.
• Option 3: If a dual stack is required, configure a static IPv6 address on vCenter.

In summary:

• Configure DNS without IPv6 information, or
• Configure vCenter with proper IPv6 information.

 

Workaround:
If immediate resolution is not possible, the following workaround can be applied to bypass the pre-check:

1. Add required static IP addresses (all VCs and PSCs) into /etc/hosts.
2. Comment out (add #) DNS servers in /etc/resolv.conf.
3. Restart the DNS service:
     #systemctl restart dnsmasq.service
4. Retry the upgrade pre-checks. It should now proceed to the next stage.
5. After completing pre-checks, re-enable DNS servers in /etc/resolv.conf by removing the #.