Whether part of a fresh installation or continue growth and expansion of an existing environment, transport zones will need to be created.
Transport zones dictate which hosts and, therefore, which VMs can participate in the use of a particular network. A transport zone does this by limiting the hosts that can “see” a segment—and, therefore, which VMs can be attached to the segment. A transport zone can span one or more host clusters. Also, a transport node can be associated to multiple transport zones.
An NSX-T Data Center environment can contain one or more transport zones based on your requirements. A host can belong to multiple transport zones. A segment can belong to only one transport zone.
The overlay and VLAN transport zone is used by both host transport nodes and NSX Edge nodes. When a host is added to an overlay transport zone, you can configure an N-VDS or a VDS switch on the host. You can only configure a N-VDS switch on NSX Edge transport nodes.
The VLAN transport zone is used by the NSX Edge and host transport nodes for its VLAN uplinks. When an NSX Edge is added to a VLAN transport zone, a VLAN N-VDS is installed on the NSX Edge.
Creating Transport Zones

System > Configuration > Fabric > Transport Zones
Add Zone
Time to create our first production overlay TZ

Currently, all we have to do is provide a name like Production-Overlay-TZ
Repeat for VLAN TZ

We will want to create a VLAN TZ to communicate with the non-overlay networks that are external to NSX-T

Confirm both TZ’s have been generated
Summary:
Creating transport zones is a simple and easy process in NSX-T. However, the proper planning and troubleshooting can be the tricky part. Remember, NSX-T does not allow connection of VMs that are in different transport zones in the Layer 2 network. The span of a segment is limited to a transport zone.