Learning NSX-T-Part 9:Creating Logical Switches and Testing Connectivity

In last post of this series we configured transport zones and transport nodes. We discussed about the modes of transport zone and also touch based on N-VDS. In this post we will learn how to create logical switches in NSX-T and we will test connectivity between vm’s attached to same logical switch.

If you are not following along this series, then I recommend reading earlier posts of this series from below links:

1: Introduction to NSX-T

2: NSX-T Architecture

3: NSX Manager Deployment

4: NSX Controllers Automated Deployment

5: NSX Controllers Manual Deployment

6: Prepare Esxi host to form NSX-T Fabric

7: Configuring Uplink Profile

8: Configuring Transport Zone and Transport Nodes

Logical switch provides layer 2 connectivity for the virtual machines that are attached to the it. In last post we discussed that transport zones are of two types (Overlay and VLAN) and the type of logical switch is based on to which type of transport zone it connects to. 

When logical switches are attached to transport zones, it connects to the N-VDS for networking. A logical switch when deployed, creates a broadcast domain to allow isolation of the VM’s running in infrastructure.

When logical switches are created, they are assigned a VNI from the pool defined by administrator. These VNI are very much similar to VLAN ID’s but have a much higher range than VLAN (4094).

Information about VNI pool can be viewed by logging into NSX manager and navigating to Home > Fabric > Profiles > Configuration. You can edit the default pool and create a custom range as per your infrastructure requirement.


Lets walk through the process of creating logical switches.

To create a new logical switch, navigate to Home > Switching > Switches and click on + Add button.


Provide a name for the switch and select the transport zone to which this logical switch can connect to.

Uplink teaming policy can be left to default for lab configuration and admin status should be set to Up.

Select the appropriate replication mode and enter VLAN id only if  the transport zone is VLAN based and not overlay.


Make sure Admin status for your logical switches reads as Up post creation and config state as success.


At vCenter level you will see these logical switches appearing as port groups but with slightly different icon than regular portgroups. These portgroups are known as opaque network in NSX-T terms.


Unlike NSX-v, I did not find any option to attach VM’s to the newly created logical switches. So to add VM’s to these, you need to edit the vm settings and change the NIC connection to these portgroups which belongs to logical switches.

To list the vm’s which are connected to a logical switch, you can click the logical switch and go to Related tab. 

I added my App and Web VM to my Dev-App-Tier logical switch and next I am gonna test the communication between the 2 vm’s.


Also if you navigate to Port Connection tab, it will show you relationship between the 2 VM’s i.e if they are connected to same or different logical switches and whether or not they are running on same host. 


Testing Logical Switch Connectivity

Now its time to test whether or not the 2 vm’s which I added on Dev-App-Tier logical switch are able to communicate with each other.

I put my App and Web VM on the network with App vm having IP and Web vm having

I initiated ping from App to my Web vm and i was able to get a ping reply. Also ARP table was populated with entry of the vm which i just pinged.


Then I pinged from Web to App vm and got a response and ARP table had now an entry of the IP and Mac address of the App-01 vm.


So we saw the connectivity between the 2 vm’s is established.

And that’s it for this post. In next post of this series we will learn about logical routing

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