How to create Logical Switches in NSX-T?

Lets discuss how to create logical switches in NSX-T. In my previous blog post, we have discussed how to configure the fabric node as a transport node. So what are logical switches?

Logical Switches:

In NSX-T, virtual layer 2 domains are called as logical switches. Logical switches are defined as part of a transport zone. There are two types of transport zones:

Overlay transport zones
VLAN transport zones

The type of the logical switch is derived from the transport zone it belongs to. Connecting an NVDS to the network is achieved by attaching it to one or more transport zones. Based on this attachment, the N-VDS has access to the logical switches defined within the transport zone(s). A transport zone defines the span of the virtual network, as logical switches only extend to N-VDS
on the transport nodes attached to the transport zone.

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

How to Check the VNI Pool?

To see and edit the VNI pool of values, log in to NSX Manager, navigate to Fabric > Profiles, and click the Configuration tab.

Note: 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.

How to create Logical Switches?

Navigate to Switching > Switches > then click +ADD

Logical-Switch-02 — **Switching > Switches > + ADD**

On the Add New Logical Switch, enter the following details in General tab:
- Name: Name of the Logical Switch
- Description: Optional description
- Transport Zone: Overlay Transport Zone or VLAN Transport Zone
- Admin Status: Up/Down
- Replication Mode: Hierarchical Two-Tier replication or Head Replication
- VLAN: VLAN ID to create a Logical Switch in a VLAN Transport Zone

Logical-Switch-04 — **Add New Logical Switch >** **General** Tab

Click on Switching Profiles tab, if you want to assign the Switching Profiles to the Logical Switch.
Click SAVE

NOTE: To create a new Switching Profile, Navigate to Switching and then Click on Switching Profiles

Logical-Switch-05 — **Add New Logical Switch >Switching Profiles** tab

After Creating the logical switch, you will see the following details for a given logical Switch.

Logical Switch Name: Name of the logical Switch
UUID: UUID of the Logical Switch
Admin Status: Up/Down
Logical Ports: Number of ports used by the Virtual Machines connecting to Logical Switch
Traffic Type:VNI: Traffic Type and the VNI ID of a Logical Switch
Config State: Configuration status of the Logical Switch (Success/Pending/Failed)
Transport Zone: Logical Switch Transport Zone

Log in to the vCenter Server with the administrator credentials and Click on Networking from the vCenter home page. Please notice the Logical Switches from the networking view, the logical Switches are Opaque networks in vSphere.

So what is Opaque Network?

An opaque network is a construct that logically connects virtual machine on the same host to each other and to the external network by using the physical network adapters on the host. Opaque networks are designed for virtual switches of types other than vSphere Standard Switch and vSphere Distributed Switch, such as NSX vSwitch.

To create and configure opaque networks on NSX vSwitch, use the nsxcli console commands in ESXi Shell.

How to connect the vSphere VMs to the Logical Switch?

Right Click on the Virtual Machine > Click Edit Settings > Connect Network adapter to Opaque networks (NSX Logical Switch). > Click OK to Save

Connecting the vSphere Virtual Machines to Logical Switches is no different than how you connect to a portgroup. Once you connect all the Virtual Machines to the Logical Switches, log in to the NSX Manager with the admin credentials, nagivate to Switching > Click Ports tab to check the logical port details.

From the Ports tab, you will see the logical port details, which includes logical port Name, UUID, Admin Status, Operational Status, Switching Profiles, Attachment ID, Logical Switch.

Lets see the T1-App-01 Virtual Machine status: