O'Reilly logo
  • Nicholas O'Neill thinks this is interesting:

Forming Spoke-to-Spoke Tunnels

From

Cover of Cisco Intelligent WAN (IWAN)

Note

Good explanation here:
http://blog.ine.com/2008/12/23/dmvpn-phase-3/

Redirect is a "Traffic Indication" which is the terminology used in debugs and Wireshark

1) Hubs in Phase 3 are not the only source of NHRP information as the resolution request from one spoke can be passed via the hub to another spoke and the destination spoke can reply directly to the source spoke.

2) NHRP replies include the a Prefix Length field so an entry can be added for the entire subnet rather than a single address (that triggered the redirect).