VMware NSX Installation and Configuration Part 8- Creating a Logical Switch

An NSX logical switch reproduces switching functionality (unicast, multicast, broadcast) 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 VXLAN if the VMs are connected to the same logical switch. Each logical switch has a segment ID, like a VLAN ID. Unlike VLAN IDs, it’s possible to have up to 16 million segment IDs.



1 In the vSphere Web Client, navigate to Home > Networking & Security > Logical Switches.

2 Click the New Logical Switch (+) icon.


3 Type a name and optional description for the logical switch.

4 Select the transport zone in which you want to create the logical switch. By default, the logical switch inherits the control plane replication mode from the transport zone. You can change it to one of the other available modes. The available modes are unicast, hybrid, and multicast. The case in which you might want to override the inherited transport zone’s control plane replication mode for an individual logical switch is when the logical switch you are creating has significantly different characteristics in terms of the amount of BUM traffic it will to carry. In this case, you might create a transport zone that uses as unicast mode, and use hybrid or multicast mode for the individual logical switch.

5 (Optional) Click Enable IP Discovery to enable ARP suppression. This setting minimizes ARP traffic flooding within individual VXLAN segments—in other words, between VMs connected to the same logical switch. IP discovery is enabled by default.

6 (Optional) Click Enable MAC learning if your VMs have multiple MAC addresses or are using virtual NICs that are trunking VLANs.


7 Attach a VM to the logical switch by selecting the switch and clicking the Add Virtual Machine (+) icon.


8 Select the VM and click the right-arrow button.


9 Select a vNIC



Each logical switch that you create receives an ID from the segment ID pool, and a virtual wire is created. A virtual wire is a dvPortgroup that is created on each vSphere distributed switch.

The virtual wire descriptor contains the name of the logical switch and the logical switch’s segment ID. Assigned segment IDs appear in multiple places, as shown in the following examples. In Home > Networking & Security > Logical Switches:


In Home > Networking:


In Home > Hosts and Clusters > VM > Summary


On the hosts that are running the VMs that are attached to the logical switch, log in and execute the following commands to view local VXLAN configuration and state information. n Displays host-specific VXLAN details.


VDS Name displays the vSphere distributed switch to which the host is attached. The Segment ID is the IP network used by VXLAN. The Gateway IP is the gateway IP address used by VXLAN.

The Network Count remains 0 unless a DLR is attached to the logical switch. The Vmknic count should match the number of VMs attached to the logical switch

Test IP VTEP interface connectivity, and verify the MTU has been increased to support VXLAN encapsulation. Ping the vmknic interface IP address, which can be found on the host’s Manage > Networking > Virtual switches page in the vCenter Web Client.


The -d flag sets the don’t-fragment (DF) bit on IPv4 packets. The -s flag sets the packet size.


This is it regarding the creation of a logical switch , in the next blog post i will cover the configuration of Distributed logical router.

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