show ntp status
Displays the current NTP synchronization status, including clock stratum, reference clock, and synchronization state, used to verify NTP operation and clock accuracy.
show ntp statusWhen to Use This Command
- Verify that a router is synchronized to an NTP server after initial configuration.
- Troubleshoot clock drift or unsynchronized state causing authentication or logging issues.
- Check stratum level to ensure the device is not using a high-stratum (less accurate) reference.
- Confirm NTP association with a specific server after network changes.
Command Examples
Synchronized NTP Status
show ntp statusClock is synchronized, stratum 2, reference is 192.168.1.10 nominal freq is 250.0000 Hz, actual freq is 249.9999 Hz, precision is 2**18 ntp uptime is 1234567 (1/100 of seconds), resolution is 4000 reference time is D3A1B2C4.12345678 (14:30:00.123 UTC Mon Jan 15 2024) clock offset is 0.1234 msec, root delay is 10.5678 msec root dispersion is 5.4321 msec, peer dispersion is 2.3456 msec loopfilter state is 'PHASE' (LOCKED)
Clock is synchronized: device is synced to an NTP source. stratum 2: device is two hops from a stratum 1 clock. reference is 192.168.1.10: IP of the NTP server. nominal/actual freq: oscillator frequency, small deviation is normal. ntp uptime: time since NTP started (in 1/100 sec). reference time: last sync timestamp. clock offset: time difference to server (should be low). root delay/dispersion: network delay and jitter to primary source. loopfilter state: 'LOCKED' indicates stable sync.
Unsynchronized NTP Status
show ntp statusClock is unsynchronized, stratum 16, no reference clock nominal freq is 250.0000 Hz, actual freq is 250.0000 Hz, precision is 2**18 ntp uptime is 0, resolution is 4000 reference time is 00000000.00000000 (00:00:00.000 UTC Mon Jan 1 2000) clock offset is 0.0000 msec, root delay is 0.0000 msec root dispersion is 0.0000 msec, peer dispersion is 0.0000 msec loopfilter state is 'SPIK' (UNSYNC)
Clock is unsynchronized: device not synced to any NTP source. stratum 16: indicates unsynchronized (max value). no reference clock: no server reachable. ntp uptime 0: NTP process not running or just started. reference time all zeros: no sync timestamp. clock offset zero: no measurement. loopfilter state 'SPIK' (UNSYNC): indicates no synchronization.
Understanding the Output
The 'show ntp status' output provides a snapshot of the NTP synchronization state. The first line is critical: 'Clock is synchronized' or 'unsynchronized'. Stratum indicates accuracy (1 is most accurate, 16 means unsynchronized). 'reference is' shows the IP of the NTP server used. 'clock offset' should be low (milliseconds) for good sync; high offset indicates delay or drift. 'root delay' and 'root dispersion' reflect network path quality; high values suggest network issues. 'loopfilter state' shows the phase-locked loop status: 'LOCKED' is good, 'SPIK' or 'UNSYNC' indicates problems. In a real network, check that stratum is not 16, offset is under a few milliseconds, and loopfilter is locked.
CCNA Exam Tips
CCNA exam tip: Stratum 16 means the device is not synchronized; this is a common distractor.
CCNA exam tip: The 'reference is' field shows the NTP server IP, not the peer IP in 'show ntp associations'.
CCNA exam tip: A high 'clock offset' (e.g., >1000 msec) indicates NTP is not working properly.
CCNA exam tip: Remember that 'show ntp status' only shows the active reference, while 'show ntp associations' shows all configured servers.
Common Mistakes
Mistake 1: Assuming stratum 16 means the device is a stratum 16 server; it actually means unsynchronized.
Mistake 2: Confusing 'reference is' with the local clock; it's the IP of the NTP server the device is synced to.
Mistake 3: Ignoring 'loopfilter state' — a 'SPIK' state indicates instability even if 'synchronized' is shown.
Related Commands
ntp server [ip]
Configures the router to synchronize its system clock with an NTP server, ensuring accurate time for logging, authentication, and network protocols.
show clock
Displays the current system date, time, timezone, and whether the time is synchronized via NTP or manually set, used to verify system time accuracy for logging, authentication, and scheduled tasks.
show ntp associations
Displays the status of NTP associations configured on the device, used to verify NTP synchronization and identify time sources.
Practice for the CCNA 200-301
Test your knowledge with hundreds of CCNA practice questions covering all exam domains.
Practice CCNA Questions