Network Time Protocol allows administrators to set the system time on all of their compatible systems from a single source, ensuring a consistent time stamp for logging and authentication protocols.

NTP is an internet standard, defined in RFC1305.

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1 – Enable NTP authentication.

hostname(config)#ntp authenticate
hostname#show run | include ntp

2 – Define an authentication key for NTP.

hostname(config)#ntp authentication-key {ntp_key_id} md5 {ntp_key}
hostname#show run | include ntp authentication-key

3 – Configure the NTP trusted key.

hostname(config)#ntp trusted-key {ntp_key_id}
hostname#show run | include ntp trusted-key

4 – Specify the authentication key for each NTP server.

hostname(config)#ntp server {ntp-server_ip_address}{key ntp_key_id}
hostname#show run | include ntp server

5 – Set the IP Address for the NTP server.
hostname(config)#ntp server {ip address}
hostname#sh ntp associations

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