NHRP is a generic protocol that converts overlay addresses in any address
family into transport addresses in any address family. The protocol works over
NBMA meaning that it can work over virtually anything (i.e. no exuberant
requirements).
There is a clean layer separation and NHRP does not
In this case we are effectively building an NBMA tunnel cloud. I.e. A bunch of
spoke nodes connected to one or more interconnected hubs. Using NHRP to find
end-points in order to build the cross tunnels makes sense. Once you have used
NHRP to find the endpoint then you can use IKE/IPsec to
