Understanding NTP

Network Time Protocol (NTP) uses UDP port 123, and it allows network devices to synchronize their time. Ideally, they would synchronize their time to a trusted time server. You can configure a Cisco router to act as a trusted NTP server for the local network, and in the same way, that trusted NTP server (Cisco router) could turn around and be an NTP client to a trusted NTP server either on the Internet or reachable via network connectivity. NTP Version 3 supports cryptographic authentication between NTP devices, and for this reason its use is preferable over any earlier versions.

One benefit of having reliable synchronized time is that log files and messages generated by the router can be correlated. In fact, if we had 20 routers, ...

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