Network upgrades can be tricky with VMware Horizon View during the network upgrade; the following must remain in place for the environment to remain operational:
Network connectivity between the vCenter and the ESXi hosts
Network connectivity between the View composer and the View connection servers
Network connectivity between the View connection servers and the virtual desktops
Network connectivity between the View connection servers and the View security servers
Network connectivity between all services and the DNS servers
Network connectivity between all services and Active Directory domain controllers
Network connectivity between the View connection servers and the clients
Network connectivity between the View security servers and the clients
Network connectivity between the ESXi hosts and any NFS or iSCSI storage
In practice, unless the upgrade can be accomplished without taking down the network, an outage will likely be required. During a network outage, the following...