NSX – Logical Switch

Next up on the NSX build out is creating logical switches! A logical switch is a distributed port group on a distributed switch. So why logical? Because it gets a unique VNI (VXLAN Network Identifier) to overlays the L2 network.

Every time you create a Logical Switch you are creating a VXLAN, a great way to think about the power of a Logical Switch is to consider how much time and paperwork is required to add a new VLAN to ESXi hosts (in a large enterprise this can take days). With NSX I can now do this in minutes.

To create a Logical Switch go to Web Client > Networking & SecurityLogical Switches then click the green plus icon.


  1. Name: The name of your switch. (This is not a naming conventions post… don’t worry)
  2. Description: As it says.
  3. Transport Zone: Select a transport zone, which will automatically select the replication mode that was associated with the transport zone.
  4. Enable IP Discovery: If you want to suppress ARP traffic, check this box.
    1. ARP (Address Resolution Protocol) requests are generated when a source knows a target’s IP address but not their MAC address. An ARP is a frame that is broadcast (destination of FFFF:FFFF:FFFF) across a layer 2 segment. NSX Controllers have the ability to maintain an ARP table for each VXLAN segment, removing the need for most ARPs.
  5. Enable MAC Learning: A handy feature to enable if your VMs have multiple MAC addresses. As per the official documentation: Enabling MAC Learning builds a VLAN/MAC pair learning table on each vNic. This table is stored as part of the dvfilter data. During vMotion, dvfilter saves and restores the table at the new location. The switch then issues RARPs for all the VLAN/MAC entries in the table.

Click OK and you will have created a new Logical Switch. Your Logical Switch will appear as a port group in your distributed vSwitch with a long auto-generated(ish) name (the name of the Logical Switch and its Segment ID are embedded towards the end of the portgroup name)

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