What is a commonality between DMVPN and FlexVPN technologies?

Explanation

In its essence, FlexVPN is the same as DMVPN. Connections between devices are still point-to-point GRE tunnels, spoke-to-spoke connectivity is still achieved with NHRP redirect message, IOS routers even run the same NHRP code for both DMVPN and FlexVPN, which also means that both are Cisco’s proprietary technologies.