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Secure Time Management

The April IP Corner article It’s good to be on time described how you can use Network Time Protocol (NTP) to synchronize the real-time clock of your network devices with external time references. As soon as you start relying on your routers having pretty exact time, NTP becomes part of your mission-critical network infrastructure and has to be protected protected against intruders or impostors.

Default NTP settings on Cisco IOS allow intruders to change the router’s time or even current year as soon as the router is not synchronized directly with a primary (stratum 1) NTP server. In the Secure Time Management article, I'm describing a very simple NTP attack on an unprotected network and the safeguards you can put in place to prevent similar attacks.
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