The size of a single VMware VPN Network with a VMware SD-WAN Hub is constrained by the scale of the individual Hub. For large networks containing thousands of remote sites, it would be preferable for both scalability and risk mitigation to use multiple Hubs to handle the Edges. However, it is impractical to mandate that the customer manage individual separate Hubs to achieve this. Clustering allows multiple Hubs to be leveraged while providing the simplicity of managing those Hubs as one common entity with built-in resiliency.

SD-WAN Edge Clustering addresses the issue of SD-WAN Hub scale because it can be used to easily expand the tunnel capacity of the Hub dynamically by creating a logical cluster of Edges. Edge Clustering also provides resiliency via the Active/Active High Availability (HA) topology that a cluster of SD-WAN Edges would provide. A cluster is functionally treated as an individual Hub from the perspective of other Edges.

The Hubs in a VMware Cluster can be either physical or Virtual Edges. If they are virtual, they may exist on a single hypervisor or across multiple hypervisors.

Each Edge in a cluster periodically reports usage and load stats to the SD-WAN Gateway. The load value is calculated based on Edge CPU and memory utilization along with the number of tunnels connected to the Hub as a percentage of the Edge model’s tunnel capacity. The Hubs within the cluster do not directly communicate nor exchange state information. Typically, Edge Clusters are deployed as Hubs in data centers.

Note: Theoretically, Edge Clustering could be used to horizontally scale other vectors, such as throughput. However, the current Edge Clustering implementation has been specifically designed and tested to scale at tunnel capacity only.