"Unrecognized network configuration flags / Cannot validate target appliance configuration as not enough information" when upgrading to VCSA 6.7

Products

• VMware vCenter Server

Issue/Introduction

Symptoms:

• Upgrading to VCSA 6.7 fails at Pre-checks at Stage-2 with the error:
  
  Cannot validate target appliance configuration as not enough information from the source appliance can be collected

• Network configuration validation fails.
• In the /var/log/vmware/upgrade/upgrade-requirements.log file, you see entries similar to:

2019-05-30T14:49:57.447Z INFO upgrade_commands Validating if source fqdn is only resolved by Autov6 address and if it will be dropped.
2019-05-30T14:49:57.447Z ERROR apply_networking Unrecognized network configuration flags 'STATICV4+NONEV6'.
2019-05-30T14:49:57.447Z ERROR upgrade_commands Unable to execute pre-upgrade checks on target machine
Traceback (most recent call last):
       File "/usr/lib/vmware/cis_upgrade_runner/bootstrap_scripts/upgrade_commands.py", line 2750, in _executeTargetPreupgradeChecks
         if self._validateNetworking(preupgradeResult):
       File "/usr/lib/vmware/cis_upgrade_runner/bootstrap_scripts/upgrade_commands.py", line 2652, in _validateNetworking
         self._hasAutov6ResolvableConflicts(sourceConfig, sourceFqdn, sourceDnsServers)
       File "/usr/lib/vmware/cis_upgrade_runner/bootstrap_scripts/upgrade_commands.py", line 1930, in _hasAutov6ResolvableConflicts
         preservedFlags, _droppedFlags = getPreservedNetFlags(sourceNetworking['config_flags'])
       File "/usr/lib/vmware/cis_upgrade_runner/bootstrap_scripts/apply_networking.py", line 410, in getPreservedNetFlags
         raise NetworkConfigError(error)
     apply_networking.NetworkConfigError: Unrecognized network configuration flags 'STATICV4+NONEV6'

Resolution

This issue is resolved in vCenter Server 6.7 U1b, available at VMware Downloads.

Workaround:
To workaround this issue:

1. Login to https://<vCenterServer_FQDN>:5480 vami page.
2. Navigate to Networking and enable IPV6 settings.
3. Select the NIC and IPv6 Settings and select Obtain IPv6 automatically through DHCP.