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350-501 Security and Services Practice Question

To secure NTP in a service provider network, which feature should be enabled on IOS XR routers to prevent time synchronization with unauthorized NTP servers?

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

NTP authentication with MD5 keys

NTP authentication ensures that the router only synchronizes with trusted servers that have the correct key. Access lists can also limit, but authentication provides cryptographic verification. NTP broadcast mode is less secure; symmetric mode is for peer-to-peer.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • NTP authentication with MD5 keys

    Why this is correct

    Authentication verifies the identity of the NTP server.

  • NTP symmetric active mode

    Why it's wrong here

    Symmetric mode is for peering, not security.

  • NTP broadcast client mode

    Why it's wrong here

    Broadcast mode does not authenticate the server.

  • NTP access group with read-only community

    Why it's wrong here

    Access groups restrict access but do not authenticate.

Visual reference

Source Router + ACL permit 10.0.0.0/8 deny any Server 10.0.0.5 ✓ 192.168.1.1 ✗ dropped ACLs evaluate top-down; first match wins — implicit deny all at end

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JA

Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

This 350-501 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-501 exam.