Implementing and Operating Cisco Enterprise Network Core Technologies (ENCOR) v1.2InfrastructureHard
A network engineer is configuring a Cisco router to synchronize its time with a reliable external source. The router is in a secure network segment and can only initiate connections outbound. The engineer wants the router to actively poll a specific NTP server and also be able to serve time to other internal devices. Which NTP mode configuration best suits these requirements?
- ANTP multicast mode
- BNTP broadcast mode
- CNTP client/server mode
- DNTP symmetric active mode
Show answer & explanationAnswer & explanation
Correct answer: D. NTP symmetric active mode
NTP symmetric active mode allows peers to both send and receive NTP packets, enabling them to synchronize with each other. In this scenario, the router can actively poll the external server (acting as a client to the server) and also serve time to other internal devices (acting as a server to them), while maintaining a peer relationship with the external source.
Why the other options are wrong
- A. NTP multicast mode is also one-way and insecure for server synchronization; it's primarily for distribution within a LAN.
- B. NTP broadcast mode is insecure and typically not used in production for server synchronization; it's one-way.
- C. NTP client/server mode describes two roles, but the 'symmetric active' specifically allows a device to both poll and be polled by a peer, which is what's implied for robust synchronization and serving.
NTP Symmetric Active Mode
An NTP operational mode where two peers actively exchange time information with each other, allowing both to synchronize and potentially serve time.
- Peers actively send and receive NTP packets to each other.
- Provides robust synchronization by allowing both devices to update each other.
- Often used between primary time servers or between a server and a highly critical client that also serves others.
Memory trick: NTP modes define how time flows: one-way, two-way, or peer-to-peer.