DMVPN Phase 2

Continuing from the previous post, let's now see how phase 2 works. 

The major difference between phase 1 and phase 2 is that in phase 2, the spokes can communicate to other spokes directly by using the NHRP mapping information from the hub.

To enable the spoke to create dynamic tunnels, we will remove the tunnel destination command and change the tunnel mode to "gre multipoint".

At the moment, we can see that R2 is learning the loopback of R3 with the next hop 10.1.1.1 (hub's tunnel IP). 

DMVPN Phase 1

As shown in the diagram below, let's assume that a customer has three sites. R1 represents the hub, R2 and R3 are the remote spokes. Each site has a local internet connection. Our aim to provide connectivity between the LAN subnets of all three sites.

The IP addresses 1.1.1.1/30, 2.2.2.1/30 and 3.3.3.1/30 are the public IPs provided by the local ISPs at respective locations. The 192.168.X.0/24 is the LAN IP subnet at each site.