In addition to this upgrade guide, VMware publishes various other documents that support the upgrade process.
Before beginning the upgrade, check the release notes. Known upgrade issues and workarounds are documented in the NSX release notes. Reading the upgrade issues before you begin the upgrade process can save you time and effort. See https://docs.vmware.com/en/VMware-NSX-for-vSphere/index.html.
Product Interoperability Matrix
Verify interoperability with other VMware products, such as vCenter. See the Interoperability tab of the VMware Product Interoperability Matrix at http://partnerweb.vmware.com/comp_guide2/sim/interop_matrix.php#interop&93=.
Upgrade Path Matrix
Verify support for the upgrade path from your current version of NSX to the version that you are upgrading to. See the Upgrade Path tab of the VMware Product Interoperability Matrix at http://partnerweb.vmware.com/comp_guide2/sim/interop_matrix.php#upgrade&solution=93.
Verify the compatibility of partner solutions with NSX at the VMware Compatibility Guide, at http://www.vmware.com/resources/compatibility/search.php?deviceCategory=security.