NTP Written Notes

These are my ‘crib notes’ that I’ve made to serve as a last minute refresher. Please forgive the grammer / spelling as I did not develop these notes with publishing in mind.


*** Theory ****

  • Stratums: How accurate the clock.3 or 4  is a good stratum
  • NTP Modes
    • Broadcast client mode: We are a client and expect to receive the time as a broadcast
      • Config-if# ntp broadcast client
      • Show ntp associations
      • Choses the best NTP based on lower stratum
    • Static client mode: We are the client and we choose who to receive it from. Most common
      • Config# ntp server tmc.edu
      • Show ntp status
    • Master mode: The router is the master clock. It receives it from atomic clock and then sends to others.
      • Config# ntp server tmc.edu
      • Config# ntp master
      • 127,127,7,1 loopback as a NTP source
    • Peer association: top-down relationship. Top master typically associates with an atomic clock on internet
      • Config# ntp peer ip
  • Timezone: need to set timezone
    • Config# clock timezone Arizona -7
    • Config# clock summer-time
    • Authentication
      • Config# ntp authentication-key 1 md5 cisco
      • Config# ntp authentication-key 2 md5 nugget
      • Config# ntp trusted-key 2



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