HCX 4.0 introduced plenty of new features and functionalities, such as migration details and security tag migrations to name a few. One of the features I like the most is In-Service Upgrade for the network extension appliance(s). While the standard upgrade re-deploys the network extension (NE) appliance, the in-service upgrade will deploy an extra appliance with a new set of IPs prior to removing the old appliance. This will allow HCX to establish a tunnel between the two new appliances and then do a switchover to minimize downtime for the extended networks.
To compare the downtime the extended networks experience using each upgrade method, I tested the impact of each one on the connectivity between two VMs while redeploying the NE appliances.