DMVPN with more than two hubs
A DMVPN implementation can have a single hub or can have two hubs as DMVPN redundancy options. Alternatively, it is possible to have three or more hubs in a DMVPN configuration. You simply have to create a third hub in the same way you created the first and second hubs, and then on the spokes make sure to add an additional NHRP map command.
If you are configuring a single cloud scenario, then it is required that there is a link between the primary hub and all of the secondary hubs. The secondary hubs act as “clients” of the primary hub and require a connection. However, you only need to create a link between each secondary hub and the primary hub.
Now if you’re implementing the dual cloud scenario, you won’t need to explicitly create a tunnel between the hubs like you do in the single cloud scenario, because in this case, the secondary hubs are not clients of the primary hub. Each hub is configured independently.