A leaf-and-spine network is the core building block for the physical network in the SDDC.

  • A leaf switch is typically located inside a rack and provides network access to the servers inside that rack, it is also referred to as a Top of Rack (ToR) switch.

  • A spine switch is in the spine layer and provides connectivity between racks. Links between spine switches are typically not required. If a link failure occurs between a spine switch and a leaf switch, the routing protocol ensures that no traffic for the affected rack is sent to the spine switch that has lost connectivity to that rack.

Figure 1. Leaf-and-Spine Physical Network Design 

A row of spine switches at the top connects to a row of leaf switches below. Each switch connects to each other switch.

Ports that face the servers inside a rack should have a minimal configuration, shown in the following high-level physical and logical representation of the leaf node.


Each leaf node has identical VLAN configuration with unique /24 subnets assigned to each VLAN.

Figure 2. High-Level Physical and Logical Representation of a Leaf Node

The high-level architecture of a leaf node includes its sample VLANs.