DMVPN
Spokes discover each other and build direct tunnels on demand.
How widely is it used?
Still around, but being replacedCisco-specific; new builds usually pick SD-WAN instead.
How it works
Multipoint GRE plus NHRP lets each spoke register with the hub and then resolve another spoke's address, so a direct spoke-to-spoke tunnel forms when needed without configuring it in advance.
Connects
Many enterprise sites
Protocols
mGRE, NHRP, IPsec
Typical users
Large enterprises, Cisco-centric WANs
Main use case
A WAN that behaves like a mesh without configuring every pair.
Advantages
- Scales far better than manual tunnels
- Direct spoke traffic without hub hairpinning
Limitations
- Largely a Cisco ecosystem
- Steep learning curve