in DMVPN Phase-2
R1#ping 2.2.2.2
step-1->R1 is going to look at his global routing table in order to know how to reach to this destination 2.2.2.2
step-2->R1 see it has a route to the dst 2.2.2.0/24 learned it from eigrp routing protocol
step-3->R1 is going to see the next-hop interface and outgoing interface and he`ll find the outgoing interface is tunnel interface which means for R1 is going to encapsulate this packet in another outer L3 header
step-4->so, R1 need to know 4 ip addresses :-
1-source outer NBMA address (10.1.13.1)
2-destination outer NBMA address (???)(unknown to R1)
3-source inner ip address (192.168.124.4)
4-destination inner ip address(2.2.2.2)(the destination 2.2.2.2 is encapsulated within another inner header because R1 learened it via tunnel0)
step-5->R1 need to know how to reach to the public ip address for the destination 2.2.2.2
step-6->R1 see that he learned it via the next hop 192.168.124.2 . ok great. R1 know where is this ip came from which means if R1 knows what is the underlay public ip address for the 192.168.124.2 that means R1 is going to use this publlic ip address for the destination 2.2.2.2
step-7->R1 going to send NHRP resolution request the the hub in oder to know the public ip address for the next hop 192.168.124.2
im going to stop at that point and focus on the step-7 which is the difference between DMVPN Phase-2 and DMVPN phase-3(maybe im wrong,idk)
in DMVPN Phase-3
R1# ping 2.2.2.2
step-1 is the same
step-2 is the same
…
step-7->unlike phase-2, phase-3 is configured with the (ip nhrp shortcut) command on the spoke R1 which means in my opinion R1 is not going to send (NHRP resoltion request)directly to the hub BUT R1 is going to send the normal ICMP packet to the hub (maybe i`m wrong)
step-8 ->once the hub sees it needs to send this packet out of the same ingress tunnel interface to R2 spoke-2 , R2 is going to discard this packet and will send back to the original source R1 (NHRP redirect)message .
step-9->once R1 received (NHRP Redirect)message and because he is configured with (ip nhrp shortcut)command R1 is going to send (NHRP resolution request) message to the hub and the hub forward it to spoke-2
my question is, in DMVPN Phase-3 step-7 ,at that point what makes R1 spoke-1 stop sending (NHRP resoltuion request)message to the hub and send it a normal icmp echo request ?
what happened here? i don`t know what is the difference at that point