Implementing and Operating Cisco Enterprise Network Core Technologies (ENCOR) v1.2InfrastructureHard
A network engineer is configuring a Cisco router to use NTP. The router needs to synchronize its clock with a highly accurate external time source. The engineer wants to ensure that the router not only receives time updates but also actively checks the accuracy and integrity of the time source and uses a fallback mechanism if the primary source becomes unreliable. Which NTP mode should be configured on the router to achieve this robust synchronization?
- AClient mode
- BServer mode
- CSymmetric active mode
- DBroadcast mode
Show answer & explanationAnswer & explanation
Correct answer: C. Symmetric active mode
Symmetric active mode is the most robust NTP mode for peers. In this mode, both devices (peers) can send and receive NTP messages to each other, allowing them to synchronize with each other and actively check the health and accuracy of their respective time sources. This provides redundancy and better accuracy than simple client/server.
Why the other options are wrong
- A. Client mode only receives time from a server, it doesn't actively check integrity or offer fallback mechanisms with peers.
- B. Server mode only provides time, it doesn't synchronize with external sources.
- D. Broadcast mode is less accurate and relies on one-way communication, not robust for critical synchronization.
NTP Symmetric Active Mode
An NTP operational mode where two peers actively exchange NTP messages with each other, allowing them to synchronize their clocks and provide robust time synchronization and redundancy.
- Both devices can send and receive NTP packets to each other.
- Provides redundancy and improved accuracy by allowing peers to validate each other's time.
- Suitable for mission-critical synchronization where multiple reliable sources are needed.
Memory trick: NTP Modes: One-Way, Two-Way, or Broadcast.