A transport zone is a user defined scope for VXLAN networking traffic. Transport zones defines which hosts/clusters will be able to participate in VXLAN based virtual networking. Transport zones acts as a container to host logical switches and Esxi host uses these logical switches to communicate among themselves or with the underlying physical infrastructure.

Transport zone is a boundary where Esxi hosts create tunnels among themselves for allowing VXLAN traffic to blow. A transport zone can be associated with one or more vSphere clusters and you can have more than one transport zone in your environment.

Prerequisite: Before creating transport zone, make sure your Esxi hosts are prepared and VXLAN has been configured already. 

Create Transport Zones

To create a new transport zone, log into the vSphere Web Client and navigate to Networking & Security > Installation > Logical Network Preparation and click on green + button.

Provide a name for the transport zone and select the appropriate replication mode (we will discuss this shortly).

Select the clusters which will be connected to this transport zone and hit OK.

Configure the control plane mode for a Transport Zone

Control plane mode dictates how NSX will replicate the VXLAN data (VTEP, ARP and MAC etc) between ESXi hosts. There are three modes a transport zone can operate in:

• Multicast: Multicast will send a single packet from a source device to multiple destinations. This option requires Protocol Independent Multicast (PIM) to be enabled on your environment as well as IGMP.
• Unicast: No special physical networking configuration is needed, unlike multicast. The NSX controller handles the control plane. The controllers control and distribute the VXLAN data to the Esxi clusters inside the configured transport zone.
• Hybrid: Hybrid is a combination of both multicast and unicast. IGMP snooping is required on the first-hop switch, however you do not need PIM. The first-hop is essentially used as a proxy to handle traffic replication in its subnet. Hybrid mode can be considered as optimized unicast mode. In this mode replication traffic is offloaded to to physical network.

Replication mode of a transport zone can be changed post creation as well. To change the replication mode of a TZ follow below steps:

a: Login to your vSphere Web Client and navigate to Networking & Security > Installation > Logical Network Preparation > Transport Zones

b: Right click the transport zone you want to modify and choose All NSX user interface plugin Actions > Edit Settings

c: Select the new replication mode for this transport zone.

Important: Make sure to select “Migrate existing Logical Switches to the new control plane mode” otherwise you will have a mix of replication modes; the existing Logical Switches will remain using the previous replication mode and newly created Logical Switches will start using the new replication mode.

Add clusters to Transport Zones

Newly created clusters are not included in a Transport Zone by default, you need to manually add any new clusters. To add a cluster to an existing Transport Zone, select the TZ and right click on it and select Connect Clusters 

Select the cluster’s which you want to add and hit OK. In below example, I added my Mgmt & Edge cluster to the existing TZ “Local-TZ-SiteA”

Remove clusters from Transport Zones

To remove a cluster from a TZ, select the TZ from list and right click on it and select “Disconnect clusters”

Select the cluster which you want to remove and hit OK.

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