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How it works...

As part of the logical switch creation, you will see a new dvPortGroup created under the vSphere networking. The logical switch is represented as a dvPortGroup on each vSphere distributed switch (vDS). The backing dvPortGroup for the logical switch naming convention is vxw-dvs-###-virtualwire-###-sid-<Segment ID>-<Logical Switch Name>:

vxw: VXLAN-VirtualWire to distinguish the dvPortGroup created by NSX
dvs-###: MoRefID of the vDS
virtualwire-###: virtualwire ID within NSX
sid-<Segment ID>: segment ID or VNI

For example, the Transit_Network_01 logical switch will have a backing dvPortGroup, vxw-dvs-38-virtualwire-1-sid-10000-Transit_Network_01, and will use the VLAN ID (VLAN 130 in this example), which was configured during the VXLAN configuration:

From NSX 6.4, the logical switch backing dvPortGroup will have VLAN ID value as none. The VLAN ID for VXLAN transport will be configured by NSX just on the VTEP VMKernel.

Logical switches can extend across multiple vSphere distributed switches if the logical switch is created on a transport zone that is spanning across multiple vDS. The backing dvPortGroup will be created in all the vDSs on that transport zone, as shown in the following example:

The detailed process of the logical switch creation is as follows:

The vSphere web client plugin for VMware NSX makes an API call to create the logical switch to the NSX Manager through TCP port 443.
The NSX Manager then makes an API call to create dvPortGroup(s) for the logical switch and pushes three vDS opaque configurations to the vCenter server:
- Control plane: com.vmware.net.vxlan.cp= 0x 0.0.0.1.
  0 = Disabled on multicast; 1 = Enabled on hybrid or unicast.
- VNI or segment ID: com.vmware.net vxlan.id = 0x 0.0.27.10.
  The VNI format is on a dotted-hexadecimal notation. In this example, VNI is 10000.
- Multicast IP address: com.vmware.net.vlxan.mcastip= 0x ef.0.0.2.
  In this example, the multicast IP address is 239.0.0.2. It will be 1 for unicast.

The NSX Manager makes a REST API call to the NSX controller cluster to create the logical switch.
This vDS opaque data can be viewed from the ESXi console, using the net-dvs -l command: