DMVPN - mappings on hub and spokes

When configuring DMVPN, one of the fundamental configurations that are applied at both the hub and the spokes are the NHRP mappings. These mappings can be either static or dynamic.

On Spokes, these mappings are static (since they only map the hub(s)) while on the hub the mappings are dynamic because there are many spokes, and those can be added and removed. For example, on a spoke, we would see this:

Spoke1(config-if)#ip nhrp map

On the hub we would see the following command applied:

Hub(config-if)#ip nhrp map multicast dynamic

Spokes only require static mappings since they use the hub to resolve the next hop IP, however, the hub needs mappings because the routing is dynamic.

Note that this is the case only for Phase 2 and Phase 3.