Configure R1 as the DMVPN Phase 1 hub using multipoint GRE and NHRP, then run EIGRP on the tunnel so the hub advertises routes between the spokes.
R1


For DMVPN Phase 1, the hub must use tunnel mode gre multipoint so multiple spokes can connect to a single tunnel interface. ip nhrp map multicast dynamic allows the hub to accept multicast registrations dynamically from any new spoke, which means additional spoke tunnels can be learned without adding static NHRP mappings on the hub.
To let R2 and R3 learn each other's EIGRP routes through R1, EIGRP must run across the tunnel interface on the hub. Disabling EIGRP split horizon on the hub is required so routes learned from one spoke are advertised back out the same multipoint tunnel toward the other spoke. Disabling next-hop-self preserves proper spoke reachability behavior through the hub in the DMVPN environment.