You need ip connectivity from the temp VC to the ESXi host that the upgraded VC is hosted.
We want to upgrade VC-CUST (192.168.1.1), in this case migrate to 6.7 from 6.5.
This CirtualCenter resides in hosted VirtualCenter VC-Provider.
VC-Provider has NO ip connectivity to customer.
VC-CUST has no IP connectivity to ESXI host (172.16.1.2)
ESXI host (172.16.1.2) has dedicated NICs with customer network and ip connection to Provider network.
Strange but look at the picture:
During the migration process you need a temp adress in customer network (192.168.1.3). Thats fine, but when you are doing the prechecks the temp VC need to connect the esxi host that ther original VirtualCenter resides (172.16.1.2). In this case this is not possible.
What I found out is that when the precheck failed I added a secondary ip to the new VirtualCenter during upgrade. Below the picture I explaine how I added secondary IP.
Add new nic to VirtualCenter (192.168.1.3)
SSH to appliance
-rw-r–r– 1 root root 106 Jun 18 11:45 10-eth0.network
cp 10-eth0.network 10-eth1.network
Save the file
systemctl restart systemd-networkd
ping esxi on provider (172.16.1.2)
Then go back to temp ip of new vc 192.168.1.3:5480 and continue with the migration.
I got some warnings that the VC should be on the same esxi host and so on, but just warning no alerts.
The migration went thru and it was upgraded to 6.7
After the upgrade i removed the file I created and deleted the extra nic on the VirtualCenter server.