The Layer 3 leaf and spine design is becoming the more adopted design for newer, more modern data center fabrics depicted in the following figure:

Figure 35.    Leaf and spine Layer 3 design

It has the following characteristics:

• L3 is terminated at the leaf, thus all the VLANs originating from ESXi hosts terminate on leaf.
• The same VLANs can be reused for each rack.
• The leaf switches provide default gateway functionality.
• The NSX T0 Gateway for the WLD peers with the leaf switches in one rack.

Advantages:

• Vendor agnostic - Multiple network hardware vendors can be used in the design.
• Reduced VLAN span across racks, thus smaller broadcast domains.
• East-west for an NSX domain can be confined within a rack with intra-rack routing at the leaf.
• East-west across NSX domains or cross-rack is routed through the spine.
• NSX Tier0 peering is simplified by peering the WLDs with the leaf switches in the rack.

Disadvantages:

• The Layer 2 VLANs cannot span racks. VxRail clusters that span racks require a solution to allow VxRail system traffic to span racks using hardware VTEPs.
• The Layer 3 configuration might be more complex to implement.