The traditional 3-tier design is based on a Layer 2 fabric, as shown in Figure 29.

Figure 29.          Traditional 3 Tier Layer 2 Fabric Design

It has the following characteristics:

• VLANs carried throughout the fabric –increases the size of the broadcast domain beyond racks if multiple racks are needed for the infrastructure and clusters span racks.
• The aggregation layer devices of each pod are the demarcation line between L2 and L3 network domains.
• Default Gateway – HSRP/VRRP at the aggregation layer
• The NSX-V ESGs or NSX-T T0 Gateway will peer with the routers at the aggregation layer.

Advantages:

• VLANs can span racks which can be useful for VxRail system VLANs like vSAN/vMotion and node discovery.
• Layer 2 design might be considered less complex to implement.

Disadvantages:

• Large clusters spanning racks will create large broadcast domains.
• Interoperability issues between different switch vendors can introduce spanning tree issues in large fabrics.
• The NSX-V ESGs or NSX-T T0 gateways for each WLD will need to peer at the aggregation layer. For large scale deployments with multiple WLDs, the configuration will become complex.
• The size of such a deployment is limited because the fabric elements have to share a limited number of VLANs 4094. With NSX, the number of VLANs could be reduced so this might not be an issue.