350-401 Question 189
Single answerA network engineer has configured multiple switches in a network to use NTP for time synchronization. However, some devices show incorrect time while others are synchronized correctly. Upon reviewing the configuration on one of the problematic devices, the engineer observes the following commands:
ntp server 10.1.1.1 ntp server 10.2.2.2 ntp authenticate ntp authentication-key 1 md5 cisco123 ntp trusted-key 2
What is the most likely cause of the issue?
- A
The NTP servers 10.1.1.1 and 10.2.2.2 are unreachable.
- B
The trusted key configured on the device does not match the key used for authentication.
- C
The 'ntp authenticate' command is not required when multiple NTP servers are used.
- D
The device requires both servers to use the same authentication key for synchronization.
Show answer and explanation
Correct answer: B
Explanation
The issue lies in the mismatch between the trusted key and the authentication key. The device is configured to trust key 2, but the authentication key is set to key 1. As a result, the device does not trust the NTP servers and fails to synchronize. This is a common configuration issue when using NTP authentication.
- A. Incorrect.
If both NTP servers were unreachable, the device would not synchronize at all, but this does not explain why synchronization works on some devices and not others.
- B. Correct.
The trusted key (key 2) does not match the key configured for authentication (key 1). This mismatch prevents the device from trusting the NTP servers, causing synchronization issues.
- C. Incorrect.
The 'ntp authenticate' command is required when using NTP authentication, regardless of the number of NTP servers configured.
- D. Incorrect.
NTP authentication does not require both servers to use the same authentication key; each server's key must simply match the configured trusted key.