I have a design issue with a WAN network. I have decided to use dual cloud dual hub single tier DMVPN topology (ref. to http://www.cisco.com/application/pdf/en/us/guest/netsol/ns171/c649/ccmigration_09186a008075ea98.pdf - "Dynamic Multipoint VPN (DMVPN) Design Guide"). I have tested in lab 2 hubs and 3 spokes, applying the mentioned technology. Everything is OK, when the primary hub fails, there is only 1-3 seconds loss (3 pings).
The problem is that each spoke and hub will have 2 service providers for WAN - primary and backup. I am still wondering which design is better and more stable to implement - using more DMVPN clouds (for the backup service provider network) or creating static IPSEC GRE tunnels in the backup links?
Is there a guide for this case?
What is the best practice in this case?
Thanks in advance,