Question

A network engineer configures a single-hub DMVPN with mGRE only on the hub. Each spoke uses a point-to-point GRE tunnel to the hub and runs EIGRP over the overlay. Users report that traffic between two spokes works, but a packet capture shows all spoke-to-spoke traffic transiting the hub router rather than flowing directly between spokes. The engineer wants dynamic direct spoke-to-spoke tunnels. Which change is required to achieve this?

Accepted Answer

Reconfigure the spokes with mGRE interfaces and configure NHRP so spokes can resolve each other's NBMA addresses (migrate to DMVPN Phase 2 or 3)

Answer

Disable EIGRP split horizon on the hub tunnel interface so spoke routes are advertised back to other spokes

Answer

Configure the hub as an NHRP next-hop-server and leave the spokes as point-to-point GRE, which enables direct tunnels automatically

Answer

Increase the NHRP hold time on the hub and enable IP redirects on the hub tunnel interface