Introduction to Transport zones in VMware NSX-T

A transport zone controls which hosts a logical switch can reach. It can span one or  more host clusters. Transport zones dictate which hosts and, therefore, which VMs can  participate in the use of a particular network. 

Collection of transport nodes that defines the maximum span of logical switches. A transport zone represents a set of similarly provisioned hypervisors, and the logical  switches that connect VMs on those hypervisors.

A Transport Zone defines a collection of hosts that can communicate with each other  across a physical network infrastructure. This communication happens over one or more  interfaces defined as a Tunnel End Point (TEP).

If two transport nodes are in the same transport zone, VMs hosted on those transport  nodes can be attached to the NSX-T logical switch segments that are also in that transport zone. This attachment makes it possible for the VMs to communicate with  each other, assuming the VMs otherwise have Layer 2/Layer 3 reachability. 

If VMs are attached to switches that are in different transport zones, the VMs cannot communicate with each other. Transport zones do not replace Layer 2/Layer 3 reachability  requirements, but they place a limit on reachability.

Fig 1.1- Transport Zones

A node can serve as a transport node if it contains at least one hostswitch. When  creating a host transport node and adding it to a transport zone, NSX-T installs a  hostswitch on the host. The hostswitch is used for attaching VMs to NSX-T logical switch  segments and for creating NSX-T gateway router uplinks and downlinks.

In previous versions of NSX, a hostswitch could host a single transport zone; configuring  multiple transport zones required multiple host switches on the node. However, as of  NSX-T 2.4 it is possible to configure multiple transport zones using the same hostswitch.

There are two types of Transport Zone in NSX-T, Overlay and VLAN:

Fig 1.2- Overlay and VLAN Transport Zones

  • Overlay transport zones: They are used for NSX-T Logical Switch segments. Network  segments created in an Overlay transport zone will utilize TEPs and Geneve  encapsulation, as explored in Module 2: Logical Switching.
  • VLAN transport zones: They are used for traditional VLAN-backed segments. Network  segments created in a VLAN transport zone function similar to a VLAN port group  in vSphere.