Deployment Guide

7 D
ell EMC Networking - Deploying VMware vSAN with OS10 Enterprise Edition | version 1.0
3 Leaf-Spine overview
The connections between leaf and spine switches can be layer 2 (switched) or layer 3 (routed). The terms
“layer 3 topology” and “layer 2 topology” in this guide refer to these connections. In both topologies,
downstream connections to servers, storage and other endpoint devices within the racks are layer 2 and
connections to external networks are layer 3.
The following concepts apply to layer 2 and layer 3 leaf-spine topologies:
• Each leaf switch connects to every spine switch in the topology
• Servers, storage arrays, edge routers and similar devices always connect to leaf switches, never to
spines
The layer 2 and layer 3 topologies each use two leaf switches at the top of each rack configured as a Virtual
Link Trunking (VLT) pair. VLT allows all connections to be active while also providing fault tolerance. As
administrators add racks to the data center, two leaf switches configured for VLT are added to each new rack.
The total number of leaf-spine connections is equal to the number of leaf switches multiplied by the number of
spine switches. Bandwidth of the fabric may be increased by adding connections between the leaf and spine
layer as long as the spine layer has capacity for the additional connections.
Spine
Leaf
Leaf-Spine architecture
Note: For additional OS10 leaf-spine information, see Dell EMC Networking L3 Design for Leaf-Spine with
OS10EE.
3.1 Physical vSAN cluster deployment within SDDC
A vSAN cluster can be deployed in either the layer 2 or layer 3 leaf-spine topology. The deployment example
presented in this document can be used in both topologies but focuses only on the relevant layer 2
configuration for vSAN operation. Administrators should reference the leaf-spine documentation linked above
for the complete data center configuration.
VMware vSAN network design for consolidated software-defined data center (SDDC) recommends isolating
vSAN traffic to its own VLAN. In most data center applications, a physical rack with a leaf pair will contain a
single vSAN cluster. Additional vSAN clusters are typically deployed to other racks, but could also exist on
the same rack using its own unique VLAN. Shown in Figure 5 is a representation of the four server nodes that
comprise the vSAN cluster connected to the top-of-rack (ToR) leaf pair. For simplicity, only the top server
node connections are shown.