Count tunnels in a mesh or hub-and-spoke overlay and work out the goodput left after encapsulation.
Tunnel count in a full mesh grows quadratically, which is why 24 nodes need 276 tunnels and 100 nodes need 4950. Capacity is scaled by the payload fraction of the encapsulated frame. Tunnel count drives control-plane state, IKE rekey load and configuration size, and it is the usual reason a full mesh has to become a hub-and-spoke or route-reflector design.
Overlay Network
full mesh tunnels = n(n − 1) ÷ 2, hub and spoke = n − 1; overlay capacity = underlay × payload ÷ (payload + encapsulation).
full mesh tunnels = n(n − 1) ÷ 2, hub and spoke = n − 1; overlay capacity = underlay × payload ÷ (payload + encapsulation). Tunnel count in a full mesh grows quadratically, which is why 24 nodes need 276 tunnels and 100 nodes need 4950. Capacity is scaled by the payload fraction of the encapsulated frame.
Tunnel count drives control-plane state, IKE rekey load and configuration size, and it is the usual reason a full mesh has to become a hub-and-spoke or route-reflector design.
This calculator takes 5 inputs: Overlay nodes, Underlay capacity per node, Encapsulation, Average packet size, Topology. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.