This demo video explains the new Hub or Cluster Interconnect feature in VMware’s 5.1 software release. Before release 5.1, clusters could not be hubs to one another. This feature allows VMware customers to create an SD-WAN network hierarchy that supports a mix of on-premises, hybrid-cloud, and multi-cloud architectures. The video discusses the role of hubs and clusters in VMware SD-WAN, reviews an existing multi-cloud cluster-to-cluster environment, and demonstrates how to add a new cluster to the network. (If you don’t see the video here, click for the YouTube link.)
What are hubs and clusters?
For simplicity and scalability, VMware SD-WAN is based on a hub-and-spoke architecture with advanced features such as dynamic branch-to-branch tunnels addressing on-demand and any-to-any reachability.
Hubs are natural aggregation points in a customer network that multiple remote locations need to access. It can be an on-premises data center, headquarters, or cloud hosted infrastructure service providers, for example. A spoke or branch location can be configured to connect to one or more hubs via SD-WAN overlay. The hub may be a single physical or virtual device or pair of devices deployed active-standby for redundancy purposes or a cluster.
A cluster is a horizontal scaling mechanism used to address the operational limits of a single edge in terms of bandwidth and overlay tunnels. Up to eight VMware SD-WAN Edges may be placed into a single cluster. A cluster is functionally treated as an individual hub from the perspective of other edges. Spoke sites are assigned to one member of the cluster and if that member fails the spoke site will be dynamically reassigned.
About the Hub or Cluster Interconnect feature
Hub or Cluster Interconnect allows hub clusters to be configured with the hub-spoke relationship to one another. It introduces a fundamental change in the SD-WAN routing protocol that allows packets to traverse more than one overlay hop in the network. This allows spoke-to-spoke communication between remote locations that don’t share a common hub.
Before the release of the Hub or Cluster Interconnect feature, only hubs that consisted of a single device or high availability (HA) pair could be configured as hubs to one another. There were two reasons for this limitation. First, a mechanism needed to be created to address the potential tunnel scale of interconnecting multiple clusters each with multiple edges in each cluster. Second, overlay routing logic needed to be added to prevent routing loops and limit the control plane overhead of redundant route advertisements.
Benefits of Hub or Cluster Interconnect
The Hub or Cluster Interconnect feature allows branch locations to use clustering for scale. Before release 5.1, only Hub sites could use clustering due to the routing limitations mentioned above.
The feature also enables the creation of a hierarchical network of hubs and clusters peering to one another. A major benefit of this is hybrid multi-cloud support. Because the cloud doesn’t support Layer 2, virtual VMware SD-WAN Edges must be deployed as a cluster to achieve redundancy. In the past, this prevented an on-premises cluster from acting as a hub or a spoke to a cloud-hosted cluster.
