Configure HA for vCenter appliance

To configure vCenter appliance (vCenter 6.5 onwards) for HA use following steps:

Login into vCenter webUI using administrator@vsphere.local account
Create a portgroup / VLAN for vCenter HA. Existing portgroups such as "VM Network" can also be used.
Click on vCenter. Go to Configure -> vCenter HA
If status is "vCenter HA is not configured", then click on "Configure" button to configure vCenter HA
Go for Basic setup
Specify IPv4 address for the vCenter for "vCenter HA" network. Two more IPs in same subnet would be required later for witness and passive nodes.
Select appropriate vCenter HA network
Specify IP addresses for passive and witness node. Here passive is almost like vCenter and takes over in case active goes down. Witness is a very small appliance just for quorum to deal with network splits.
In "Select deployment configuration" try to use different storages for different vCenter nodes (active, passive and witness), if available. These appliances are automatically distributed across 3-hosts due to anti-affinity rules. Hence, it is important to have at least 3 hosts in cluster for configuring vCenter HA
Complete the wizard after which vcenter will clone itself for passive node and create a witness appliance also with specified IP addresses. The current vCenter management IP and network would remain same. If active appliance fails then passive will acquire this floating IP and vcenter would remain accessible.

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