DMVPN Phase 2 and Phase 3 are identical however in Phase 3, there is no need for the command "no ip next-hop-sef eigrp 10".
To implement Phase 3, we will have to configure one additional command "ip nhrp redirect" on the hub and one additional command on the spokes ""ip nhrp shortcut".
The idea here is that when a spoke try to send packets to another spoke, the initial packet will be forwarded to the hub. Upon receiving the packet on mGRE interface, hub will reply back with an "NHRP Redirect" packet which will indicate that the spoke is not using an optimal path and it should look for alternate way by using NHRP reosolution.
The spoke will then sends an NHRP request directly to the destination spoke address (not the hub). The destination spoke will reply abck with the IP routing prefix. When the source spoke receives this reply, it will then know the NBMA IP address of the destination.
