DMVPN Routing Considerations
Routing over DMVPN is probably the most important decision you should take for the VPN design.
Which routing protocol is suitable for your environment ? EIGRP over DMVPN , OSPF over DMVPN or BGP over DMVPN?
Let me just share some brief information about the routing protocol over the overlay tunnels in this post.
The best routing protocol over DMVPN is BGP or EIGRP for the large scale DMVPN deployments.
What is large depends on your links, stability, how is the redundancy, how many routes spokes have, which phase is in use and so on.
If you have 20.000 routes in total behind all your spokes, unless you are doing SLB design for your HUB, only BGP can support that number of routes.
As I stated earlier in this post, IS-IS cannot be used with DMVPN since it doesn’t run on top of IP. So forget about it!