Orhan Ergun 3 Comments


DMVPN vs. GETVPN – In this post I am going to cover the similarities and the differences between GETVPN and the DMVPN.

For the DMVPN basics, please read this post.

Both technologies provide overlay virtual private network in general and I will use the below comparison table and the design attributes listed in it. For the more technology comparison tables please click here. Read more

Orhan Ergun No Comments

DMVPN Point-to-Point GRE and mGRE

DMVPN spokes can use either point-to-point GRE tunnels or multipoint GRE tunnel interface. Recently, I received a question regarding DMVPN.

In fact, the Reader asked me two questions: When is GRE used in network design? When is mGRE used in network design?

Answering the aforementioned questions are the basics that you must know if you are planning to design DMVPN network.

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Orhan Ergun No Comments

Routing over DMVPN

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!

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Orhan Ergun 21 Comments

DMVPN Basics

In this article you will learn about the DMVPN design along with various IGP protocols such as EIGRP,OSPF and BGP.


DMVPN uses two major technologies for its operation :


  1. NHRP Next Hop Resolution Protocol
  2. mGRE Multipoint GRE

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