Configuring Ntp Authentication - Cisco NCS 6000 Series Configuration Manual

Implementing NTP
Command or Action

Configuring NTP Authentication

This task explains how to configure NTP authentication.
No specific command enables NTP; the first NTP configuration command that you issue enables NTP.
Note
The encrypted NTP authentication scheme should be used when a reliable form of access control is required.
Unlike the access-list-based restriction scheme that is based on IP addresses, the encrypted authentication
scheme uses authentication keys and an authentication process to determine if NTP synchronization packets
sent by designated peers or servers on a local network are deemed as trusted, before the time information that
it carries along is accepted.
The authentication process begins from the moment an NTP packet is created. A message authentication code
(MAC) is computed using the MD5 Message Digest Algorithm and the MAC is embedded into an NTP
synchronization packet. The NTP synchronization packet together with the embedded MAC and key number
are transmitted to the receiving client. If authentication is enabled and the key is trusted, the receiving client
computes the MAC in the same way. If the computed MAC matches the embedded MAC, the system is
allowed to sync to the server that uses this key in its packets.
After NTP authentication is properly configured, your networking device only synchronizes with and provides
synchronization to trusted time sources.
SUMMARY STEPS
1. configure
2. ntp
3. authenticate
4. authentication-key key-number md5 [clear | encrypted] key-name
5. trusted-key key-number
6. Use one of the following commands:
• end
• commit
System Management Configuration Guide for the Cisco NCS 6000 Series Router, Release 5.0.x
Purpose
◦ Entering cancel leaves the router in the current configuration
session without exiting or committing the configuration
changes.
• Use the commit command to save the configuration changes to
the running configuration file and remain within the configuration
session.
Configuring NTP Authentication
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