Exam 300-730 topic 1 question 134 discussion

The feature that allows a DMVPN Phase 3 spoke to switch to an alternate hub when the primary hub is unreachable is "backup NHS" (Next Hop Server). In DMVPN Phase 3, the spoke routers register with a Next Hop Server (NHS) to obtain the routing information for other spokes in the network. The backup NHS feature allows a spoke to have multiple NHSs configured, where the primary NHS is the preferred hub, and the backup NHSs act as alternatives. If the primary hub becomes unreachable, the spoke router will automatically switch to using one of the configured backup NHSs as the new hub. This ensures that the spoke can maintain connectivity and continue routing traffic even if the primary hub goes offline. On the other hand, NHRP (Next Hop Resolution Protocol) shortcuts are used in DMVPN to dynamically establish direct spoke-to-spoke tunnels, bypassing the hub router. NHRP shortcuts improve efficiency and reduce latency by allowing spokes to communicate directly with each other. However, it is the backup NHS feature that specifically addresses the issue of switching to an alternate hub in case of primary hub unavailability.

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B Is correct

The DMVPN-Tunnel Health Monitoring and Recovery (Backup NHS) feature allows you to control the number of connections to the Dynamic Multipoint Virtual Private Network (DMVPN) hub and allows you to switch to alternate hubs in case of a connection failure to the primary hubs. https://www.cisco.com/en/US/docs/ios-xml/ios/sec_conn_dmvpn/configuration/15-2mt/sec-conn-dmvpn-backup-nhs.html#:~:text=The%20DMVPN%2DTunnel%20Health%20Monitoring%20and%20Recovery%20(Backup%20NHS),failure%20to%20the%20primary%20hubs.