The VxRail external management network and any external-facing networks that are configured for VxRail must have routing services that support connectivity to external services and applications, and end users.
A leaf-spine network topology in the most common use case for VxRail clusters. A single VxRail cluster can start on a single pair of switches in a single rack. When workload requirements expand beyond a single rack, expansion racks can be deployed to support the additional VxRail nodes and switches. The ToR switches which are positioned as a leaf layer, can be connected using switches at the adjacent upper layer or spine layer. If you use spine-leaf network topology to support the VxRail clusters in your data center, you can enable Layer 3 routing services at either the spine layer or the leaf layer.
Establishing routing services at the spine layer means that the uplinks on the leaf layer are trunked ports, and pass through all the required VLANs to the switches at the spine layer. This topology has the advantage of enabling the Layer 2 networks to span across all the switches at the leaf layer. This topology can simplify VxRail clusters that extend beyond one rack, because the Layer 2 networks at the leaf layer do not need Layer 3 services to span across multiple racks. A major drawback to this topology is scalability. Ethernet standards enforce a limitation of addressable VLANs to 4094, which can be a constraint if the application workload requires a high number of reserved VLANs, or if multiple VxRail clusters are planned.