Building a Multi-Level NTP Hierarchy

Bundle lab · $29.99

Create a deterministic three-tier NTP hierarchy on a single shared LAN. R1 is the authoritative clock (ntp master 2), R2 syncs to R1, and R3 syncs to R2. No routing or additional subnets — all devices share 10.0.0.0/24 via one L2 switch. Verify with show ntp status and show ntp associations.

Learning objectives

• Design and configure a three-tier NTP hierarchy on a flat LAN.
• Make a router an authoritative clock with ntp master <stratum> and explain stratum behavior.
• Chain NTP clients so each device syncs to the tier immediately above it.
• Verify NTP associations and expected stratum values deterministically without waiting for convergence.
• Differentiate ntp server (client/server) from implicit serving behavior once a device is synchronized.
• Apply disciplined verification using show ntp status and show ntp associations.

Troubleshooting focus

• If a tier does not show the expected stratum, confirm it points to the correct upstream IP and that upstream is configured with ntp master <stratum> (R1) or ntp server <ip> (R2).
• Check interface status and addressing on Ethernet0/0 across R1, R2, R3 — all must be up/up in 10.0.0.0/24.
• Avoid ntp peer in this hierarchy — use ntp server to form a strict parent-child chain.
• Verify no ntp access-group restrictions are unintentionally blocking associations (not used in this lab).
• Remember that live synchronization takes time — grade by configuration, not the star in show ntp associations.