What is a Dynamic Multipoint VPN (DMVPN)?

A dynamic multipoint VPN offers organizations an innovative way to streamline network operations. Imagine connecting multiple branch offices to your central corporate hub without the tedious task of setting up point-to-point links at each site. This article covers what a DMVPN is, how it works, its advantages, and everything else you should know if you’re considering setting one up.

What is a Dynamic Multipoint VPN (DMVPN)?

A dynamic multipoint virtual private network (DMVPN) is a secure network that exchanges data between sites/routers without passing traffic through an organization’s virtual private network (VPN) server or router, located at its headquarters. A DMVPN allows organizations to build a VPN network with multiple sites, without the need to configure devices statically.

VPNs connect each remote site to the company headquarters. A DMVPN creates a mesh VPN topology. In this “hub and spoke” mesh, each remote site’s router is configured to connect to the company’s VPN hub device to provide access to the required resources.

At the same time, each site (“spoke”) can connect directly with all other spokes, irrespective of their location without having to go through the hub.

How does a DMVPN work?

A Dynamic Multipoint VPN works by allowing branch locations to communicate directly with each other over a public WAN or internet connection. In this setup, each remote site is configured with VPN routers and firewall concentrators to connect to the company’s headquarters VPN hub.

When two spokes need to exchange data, such as during a VoIP (voice over IP) call, one spoke contacts the hub to obtain information about the other spoke’s current dynamic IP address. Once the initiating spoke has the destination IP address, it can establish a dynamic IPsec VPN tunnel directly with the other spoke. This setup bypasses the need for a permanent VPN connection by utilizing a centralized hub-and-spoke model.

Traditional VPN connections between spokes and the hub involve permanent spoke-to-hub tunnels, but a DMVPN introduces a dynamic approach by creating on-demand spoke-to-spoke tunnels. These dynamic IPsec VPN tunnels are established only when needed.

What is DMVPN used for?

A Dynamic Multipoint VPN is a networking solution that allows for secure communication between multiple sites as well as remote users. This type of network offers more flexibility and scalability than traditional VPNs, as it doesn’t require pre-configured connections or static IP addresses.

Additionally, it allows for dynamic routing and support for multicast traffic to optimize network performance. As such, it is often used by companies with multiple offices or a mobile workforce that need efficient and secure communication capabilities. It can also connect multiple campuses or locations in educational settings or government institutions.

The Need For Dynamic Multipoint Virtual Private Network (DMVPN)

Let us consider an example, for instance, a company has 200 branch locations that are connected to the head office. Without Dynamic Multipoint VPN, we have to configure 200 point-to-point GRE tunnel interfaces on the Head office router, with each interface requiring at least seven lines of configuration code, therefore a total of 1400 lines of code on the Head office router, plus configuring each branch office router. The new addition of the branch office needs to configure an additional tunnel interface on the Head office router.

The DMVPN requires only one interface configuration on the Head office router to connect 200 branch offices with fifteen lines of code. The new branch office addition doesn’t require any change in the configuration of the Head office router.

The direct spoke-to-spoke VPN deployment provides some benefits over the normal VPN deployments, such as:

• Direct spoke-to-spoke traffic flow.
• Eliminates additional bandwidth requirements at the hub.
• Eliminate additional network delays.
• Conserve WAN
• They lower capital and operational expenses
• They increase resiliency and redundancy.
• Simplifies branch communications.

DMVPN Components

• Multiple GRE tunnel interfaces: a single GRE interface that can secure several IPsec tunnels, reducing the overall scope of the DMVPN configuration
• IPsec tunnel endpoint discovery: meaning that static crypto maps between individual IPsec tunnel endpoints do not have to be configured
• Routing Protocols: which can allow the DMVPN to find routes between different endpoints much more effectively
• NHRP: which can deploy spokes with assigned IP addresses that can then be connected to from the central DMVPN hub.

Conclusion

Dynamic Multipoint VPN (DMVPN) is a powerful solution for secure and scalable network connectivity across geographically dispersed locations. Its dynamic approach streamlines network management, optimizes bandwidth usage, and enhances overall network resilience. By leveraging a combination of key technologies, DMVPN facilitates efficient and secure communication between branch offices and remote users.

Looking ahead, DMVPN’s adaptability positions it for a prominent role in the future of secure networking. Its ability to integrate with emerging technologies like SDN and NFV promises even smarter and more flexible network management, allowing organizations to build secure and efficient networks that seamlessly adapt to their evolving needs.