An ESXi host reboot is not required for the following tasks:

• NSX 6.3.x to NSX 6.3.x upgrades on ESXi 6.0 or later.
• NSX 6.3.x VIB install after upgrading ESXi from 6.0 to 6.5.0a or later. The ESXi upgrade itself still requires a host reboot.
• NSX 6.3.x VIB uninstall on ESXi 6.0 or later.

An ESXi host reboot is required for the following tasks:

• NSX 6.2.x or earlier to NSX 6.3.x upgrades on any ESXi version
• NSX 6.3.0 to NSX 6.3.x upgrades on ESXi 5.5
• NSX 6.3.x VIB install after upgrading ESXi from 5.5 to 6.0 or later
• NSX 6.3.x VIB uninstall on ESXi 5.5