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An SD-WAN overlay network can be managed by one Cisco SD-WAN Manager, or it can managed by a cluster, which consists of a minimum of three Cisco SD-WAN Manager instances.
It is recommended that you build a network, especially a larger network, with a Cisco SD-WAN Manager cluster. The Cisco SD-WAN Manager manages all the Cisco vEdge devices in the overlay network, providing dashboard and detailed views of device operation, and controlling device configurations and certificates.