An NSX-T Data Center logical switch reproduces switching functionality, broadcast, unknown unicast, multicast (BUM) traffic, in a virtual environment completely decoupled from underlying hardware.

NSX Cloud Note: If using NSX Cloud, see How to use NSX-T Data Center Features with the Public Cloud for a list of auto-generated logical entities, supported features, and configurations required for NSX Cloud.

Logical switches are similar to VLANs, in that they provide network connections to which you can attach virtual machines. The VMs can then communicate with each other over tunnels between hypervisors if the VMs are connected to the same logical switch. Each logical switch has a virtual network identifier (VNI), like a VLAN ID. Unlike VLAN, VNIs scale well beyond the limits of VLAN IDs.

To see and edit the VNI pool of values, log in to NSX Manager, navigate to Fabric > Profiles, and click the Configuration tab. Note that if you make the pool too small, creating a logical switch will fail if all the VNI values are in use. If you delete a logical switch, the VNI value will be re-used, but only after 6 hours.

When you add logical switches, it is important that you map out the topology that you are building.

Figure 1. Logical Switch Topology
Logical switch with two VMs attached.

For example, the topology shows a single logical switch connected to two VMs. The two VMs can be on different hosts or the same host, in different host clusters or in the same host cluster. Because the VMs in the example are on the same virtual network, the underlying IP addresses configured on the VMs must be in the same subnet.