VLANs specific to VMware NSX-T Data Center VMware NSX-T Data Center on VxBlock Systems requires additional VLANs for the ToR switch pair. Overlay VLAN The Overlay VLAN carries all east-west data flows for overlay traffic between transport nodes. For VMware NSX-T Data Center on VxBlock System deployments, this network is defined as Layer 3 routable. If the use case requires transport nodes that are spread across multiple ToR switch pairs, the boundary between Layer 2 and Layer 3 is at the ToR switch pair. A VLAN cannot span that boundary. Examples include: A single-site multisystem deployment of VMware NSX-T Data Center A future multisite deployment of VMware NSX-T Data Center In these use cases, each L2 domain (ToR switch pair) must provision a unique subnet to hold the TEP IP addresses for the connected transport nodes. The transport nodes for each transport network subnet need to reach the other transport network subnets in the VMware NSX-T Data Center deployment. A routable transport network ensures that deployments are flexible and extensible for all current and future use cases. Uplink1 VLAN The Uplink1 VLAN enables BGP peering between the Tier-0 Gateway in the edge VM and the ToR Cisco Nexus 9000 Series switch on the A side of the network fabric. Uplink2 VLAN The Uplink2 VLAN enables BGP peering between the Tier-0 Gateway in the edge VM and the ToR Cisco Nexus 9000 Series switch on the B side of the network fabric. VRF Uplink VLANs If the VRF-lite option is deployed, an additional pair of uplink VLANs is provisioned for each VRF that is configured. These VLANs are trunked between the corresponding T0-VRF Gateway and the ToR Cisco Nexus 9000 Series Switch. Each VRF has a unique set of BGP peerings between the Tier-0 gateway and ToR switch.