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. Logical switches are local to a single vCenter NSX deployment. In a cross-vCenter NSX deployment, you can create universal logical switches, which can span all vCenters. The transport zone type determines whether the new switch is a logical switch or a universal logical switch.
When you create a logical switch, in addition to selecting a transport zone and replication mode, you configure two options: IP discovery, and MAC learning.
IP discovery 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.
You cannot disable IP discovery when you create a universal logical switch. You can disable IP discovery via the API after the universal logical switch is created. This setting is managed separately on each NSX Manager. See the NSX API Guide.
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. You might want to enable MAC learning if you are using virtual NICs that are trunking VLANs.
Universal Logical Switch
Determine the appropriate NSX Manager on which to make your changes.
In a standalone or single vCenter NSX environment there is only one NSX Manager so you do not need to select one.
Universal objects must be managed from the primary NSX Manager.
Objects local to an NSX Manager must be managed from that NSX Manager.
In a cross-vCenter NSX environment that does not have Enhanced Linked Mode enabled, you must make configuration changes from the vCenter linked to the NSX Manager that you want to modify.
In a cross-vCenter NSX environment in Enhanced Linked Mode, you can make configuration changes to any NSX Manager from any linked vCenter. Select the appropriate NSX Manager from the NSX Manager drop-down menu.
- Navigate to Home > Networking & Security > Logical Switches.
- Select the NSX Manager on which you want to create a logical switch. To create a universal logical switch, you must select the primary NSX Manager.
- Click the New Logical Switch ().
- Type a name and optional description for the logical switch.
- Select the transport zone in which you want to create the logical switch. Selecting a universal transport zone will create a universal 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.
If you create a universal logical switch and select hybrid as the replication mode, you must ensure that the multicast address used does not conflict with other multicast addresses assigned on any NSX Manager in the cross-vCenter NSX environment.
- (Optional) Click Enable IP Discovery to enable ARP suppression.
- (Optional) Click Enable MAC learning
Logical Switch and Universal Logical Switch
App is a logical switch connected to a transport zone. It is available only on the NSX Manager on which it was created.
Universal-App is a universal logical switch connected to a universal transport zone. It is available on any of the NSX Managers in the cross-vCenter NSX environment.
The logical switch and the universal logical switch have segment IDs from different segment ID pools.
What to do next
Add VMs to a logical switch or universal logical switch.
Create a logical router and attach it to your logical switches to enable connectivity between VMs that are connected to different logical switches.
Create a universal logical router and attach it to your universal logical switches to enable connectivity between VMs that are connected to different universal logical switches.