Your IWAN topology will most likely consist of one or more internet connections which means that your data will be traveling over untrusted connections and shared environments so security is going to be top of mind. So how do you secure your data over the internet and other untrusted or shared environments? Well DMVPN (Dynamic Multi-point Virtual Private Network) is based on VPN the same technology that many of you use today to securely connect back to your office when you are traveling or working from home. A VPN will create a tunnel between two end-points and then encrypt all data traveling over the tunnel. VPN’s can connect users to a remote site, client-to-site VPN, or connect two remote sites, site-to-site VPN. Unlike VPN, DMVPN can securely connect multiple points together dynamically.
So how does DMVPN work and what is the benefit to IWAN? DMVPN works on top of your WAN infrastructure which means that DMVPN tunnels will be established between branch sites as traffic flow demands. In a common hub and spoke topology example, when data needs to be sent from the spoke to the hub site, the spoke will establish a VPN tunnel to the hub by registering first with the hub. In order for each tunnel to function a new dynamic IP address is created at the branch since the hub site will initiate the connection. In order for data to be routed between sites over the DMVPN tunnels, routing information will need to be exchanged. As more tunnels are created there will be more dynamically created IP addresses and traditional routing protocols like BGP or EIGRP are used to efficiently share routing information so all sites can talk to each other. Lastly QoS is applied to each tunnel to ensure that the hub site does not oversubscribe the spoke sites.