Symptoms
vCenter Appliance 6.5 to 6.7 Upgrade is stuck at Stage 2 at Pre-Checks vCenter is deployed using IP as PNIDIPv6 is disabled on vCenter Error stack seen in PreChecks stage on Phase 2 where IP of vCenter is 192.168.0.1:
"Error: The source machine hostname '192.168.0.1' resolves to IPv6 address(es) '::ffff:192.168.0.1', but IPv6 networking will not be preserved after the upgrade. This will prevent certain services preferring IPv6 from establishing network communication.ResolutionEither remove the DNS IPv6 entry for hostname '192.168.0.1' or change the network configuration of the source machine to pure IPv6 or in case dual networking stack is needed, set a static IPv6 address."
Command below return values with both ipv4 and ipv6 format (::ffff:IP)
dig@127.0.0.1 +short VC_IP A VC_IP AAAAfor example below command returns DNS information from localhost:dig @127.0.0.1 +short 192.168.0.1 A 192.168.0.1 AAAAfor example below command returns DNS information where DNS is 192.168.0.100:dig @192.168.0.100 +short 192.168.0.1 A 192.168.0.1 AAAA192.168.0.1::ffff:192.168.0.1
Cause
Upgrade scripts checks for IPv6 resolution and if seen it will check for configuration of IPv6 on vCenter side. If it's not enabled, it will fail with above error.
Resolution
As stated, resolution is from the error stack:
Either remove the DNS IPv6 entry for hostname '192.168.0.1' or change the network configuration of the source machine to pure IPv6 or in case dual networking stack is needed, set a static IPv6 address.
As per above the options are:
Configure DNS without IPv6 information or Configure the vCenter to have also IPv6 information
Workaround
Steps to workaround the pre-check:
Add required static IP addresses into /etc/hosts file (all VC and PSC's needed)Comment (hash) DNS servers in /etc/resolv.confRestart dnsmasq service by using systemctl restart dnsmasq.serviceRetry the prechecks page which should now allow you to go to next page Add/enable DNS servers back in /etc/resolv.conf by removing the hash sign
