Resolved! EIGRP neighboring failure in DMVPN
According to the topology, R1 is hub while R2 & R3 are spokes. R4 is only used for underlay connectivity R1 configuration: interface Loopback0 ip address 172.16.1.1 255.255.255.0interface Tunnel0 ip address 192.168.1.1 255.255.255.0 ip nhrp map mu...