Overview
This lecture demonstrates configuring Network Time Protocol (NTP) on Cisco routers, covering manual and NTP-based synchronization, authentication, and verification commands for the CCNA exam.
Setting Date, Time, and Timezone
- Manually set the time on R1, R2, and R3 to 12:00 PM, December 30, 2020, in UTC.
- Configure the time zone using
clock timezone JST 9 to set JST as UTC+9 on all routers.
- Use
show clock detail to verify the time and source.
NTP Configuration and Synchronization
- Configure R1 to synchronize to NTP server 1.1.1.1 (SRV1) using
ntp server 1.1.1.1.
- Verify NTP associations with
show ntp associations; R1 becomes stratum 2 after syncing to a stratum 1 server.
- On loss of external sync, configure R1 as a backup NTP master with
ntp master (default stratum 8).
- R1 acts as NTP server for R2 and R3.
NTP Authentication Setup
- Enable NTP authentication with
ntp authenticate on all routers.
- Create an authentication key using
ntp authentication-key 1 md5 <password>.
- Set the key as trusted:
ntp trusted-key 1.
- On R2 and R3, configure R1 as their NTP server with authentication:
ntp server <R1 address> key 1.
NTP Calendar Update
- Use
ntp update-calendar to sync the router hardware calendar with NTP time (not fully supported in Packet Tracer).
Verifying and Troubleshooting NTP
- Use
show ntp status and show ntp associations to confirm synchronization and stratum levels.
- Source of time changes to NTP after successful sync; check with
show clock detail.
Boson NetSim NTP Lab Overview
- Tasks include initial configuration, setting date/time, configuring NTP master/client, and verifying synchronization.
- Specify NTP master stratum with
ntp master 3.
- Each router synchronizes to the specified peer; stratum increases by 1 per hop.
- Reference peer addresses differ by router, based on their sync source.
Key Terms & Definitions
- NTP (Network Time Protocol) — protocol for synchronizing clocks across network devices.
- Stratum — hierarchy level in NTP; lower number = closer to time source.
- NTP Authentication — security feature using keys to verify NTP sources.
- NTP Master — router that provides time to others if no upstream source is available.
- NTP Client — a device configured to receive time from an NTP server.
- NTP Calendar Update — synchronizes router’s hardware clock with NTP.
Action Items / Next Steps
- Replicate the configurations in Packet Tracer or Boson NetSim for hands-on practice.
- Review related NTP commands and output interpretation.
- Complete any assigned labs on NTP synchronization and verification.