There is a one-to-one mapping between NSX Manager and vCenter Server in version 6.1.x. Should the inventory of a portion of the hybrid cloud exceed the limits supported by a single vCenter Server, a new NSX Manager must be deployed along with any new vCenter Server added. Transport zones can be extended and scaled larger by adding more vSphere compute and NSX Edge clusters until vCenter Server limits are reached. There is a limit of 1,000 distributed logical routers per ESXi host when using NSX for vSphere 6.1.2 and above. As a design consideration, if you want to exceed the 1,000 distributed logical router limit in a VMware NSX domain, you must create multiple transport zones with different clusters in each transport zone. There are many factors that determine the scalability limits in NSX for vSphere 6.1.x and 6.2, as well as other vCenter Server limits which will likely be exceeded before reaching the limit on the NSX for vSphere components.