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IntermediatePublished 2026-07-04

CCNA NTP: Symmetric Active Peers on a /30

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Configure two Cisco IOS routers as symmetric-active NTP peers over a single /30 link. R1 is an authoritative clock (ntp master 4) and both routers form a symmetric peer relationship with ntp peer. Learn how peer mode differs from client/server, and how to verify and troubleshoot associations without relying on Internet sources.

Track
Est. time
30 minutes
Difficulty
Intermediate
Topics

Learning objectives

  • Differentiate ntp server (client/server) from ntp peer (symmetric-active)
  • Configure an authoritative clock using ntp master 4 on R1
  • Form symmetric NTP peer associations between R1 and R2
  • Verify associations with show ntp associations and interpret peer mode
  • Troubleshoot common NTP peering issues in a flat, single-subnet topology

Troubleshooting focus

  • Association present but wrong mode (server vs peer): verify use of ntp peer on both routers
  • No association at all: check interface status, IP addressing, and L2 link
  • Drift or no tracking: confirm R1 is authoritative (ntp master 4) so peers have a selectable source

Topology

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How this lab is graded
  • Build it your way. Where a lab lets you choose a value — a VLAN name, an interface description — grading checks that you configured it, not which name you picked. Names that another line has to reference, like an ACL applied with access-class, are stated in the guide and do have to match.
  • Addresses, modes and protocol keywords are exact. An IP address, a subnet mask, switchport mode trunk, an encapsulation — these carry the meaning of the lab, so they are graded as written in the guide.
  • Grading reads your saved configuration. Export the lab from CML after you have configured it, and make sure anything you set is in the running-config — a change that only exists in a terminal session never reaches the grader.
  • You can submit as many times as you like. Your best score stands, and each attempt tells you which checks passed so you can work the gaps.
  • Scored something you believe is correct? Use Report an issue on this page — that is exactly how the grading fixes in the changelog got found.

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