We are planning to process with NSX to vSphere to NSX-T migration.
This article will be focused on multisite implementation.
If you have Standalone NSX-V implemetation, this article is not for you.
We have two site NSX-V (Cross-vCenters). Unfortunately, when we try to test the migtarion using the migration coordinator, we stuck solution it fails as it is not a supported connection.
It is related to universal objects that not able to be migrated due to miltisite implementation.
Migration of a true Cross-vCenter NSX for vSphere deployment with a primary NSX Manager and multiple secondary NSX Managers is not supported yet. However, if either the primary or secondary NSX Manager is set to a standalone or transit mode, the migration is supported.
We had further issue once we set the site as standalone, and had some issues with universal objects.
Fortunately for us, starting in NSX-T 3.1.1, migration of a single universal objects on the primary site, is supported.
Hope it helps.