One of my readers sent me the following question a few days ago:
Do you have a webinar that covers Dual DMVPN HUB deployment using OSPF? If so which webinar covers it?
I told him that the DMVPN: From Basics to Scalable Networks webinar covers exactly that scenario (and numerous others), describing both Phase 1 DMVPN and Phase 2 DMVPN design and implementation guidelines. Interestingly, he replied that the information on this topic seems to be very scant:
There is very little information about how to accomplish a dual hub, dual cloud DMVPN using OSPF. ("Maybe for good reasons?")
I can’t see a good reason why you wouldn’t do that (assuming you keep the number of remote sites reasonably low and use a stub/NSSA area over DMVPN) and the “little information” part is definitely fixed in my DMVPN webinar. Even more, you get twenty sets of tested router configurations, covering everything from simple OSPF/BGP/EIGRP/RIP/ODR designs to IPsec offload and Inter-AS MPLS/VPN over Phase 2 DMVPN.
Speaking of dual-hub designs, there is a slight gotcha: if you’re running Phase 1 DMVPN and using P2MP OSPF, it doesn’t matter if you place both hub routers in the same DMVPN cloud. You’re way better off putting each hub in its separate DMVPN cloud (and IP subnet) in Phase 2 DMVPN or you’ll eventually get hit by the NHRP convergence issues which can disrupt the DMVPN traffic for up to three minutes.