Table 39-1 shows the default NTP configuration. Other machines synchronize to that machine using NTP. If the network is isolated from the Internet, Cisco's NTP implementation allows a machine to be configured so that it acts as though it is synchronized using NTP, when it actually has determined the time using other methods. We recommend that you obtain the time service for your network from the public NTP servers available on the IP Internet. With this alternative, you can configure the machine to send or receive broadcast messages, but the accuracy of timekeeping is marginally reduced because the information flow is one-way only.Ĭisco's implementation of NTP does not support stratum 1 service it is not possible to connect to a radio or atomic clock. However, in a LAN environment, you can configure NTP to use IP broadcast messages. An associated pair of machines can keep accurate timekeeping by exchanging NTP messages between each other. The communications between machines running NTP, known as associations, are usually statically configured each machine is given the IP addresses of all machines with which it should form associations. NTP compares the time that is reported by several machines and does not synchronize to a machine whose time is significantly different from the others, even if its stratum is lower.NTP never synchronizes to a machine that is not synchronized itself.NTP has two ways to avoid synchronizing to a machine whose time might be ambiguous: This strategy effectively builds a self-organizing tree of NTP speakers. A machine running NTP automatically chooses as its time source the machine with the lowest stratum number that it is configured to communicate with through NTP. A stratum 1 time server has a radio or atomic clock that is directly attached, a stratum 2 time server receives its time from a stratum 1 time server, and so on. NTP uses a stratum to describe how many NTP hops away a machine is from an authoritative time source. NTP is extremely efficient no more than one packet per minute is necessary to synchronize two machines to within a millisecond of one another. NTP distributes this time across the network. An NTP network usually gets its time from an authoritative time source, such as a radio clock or an atomic clock that is attached to a time server. Lastly, use the timestamp() to convert the datetime object, in UTC, to get the UTC timestamp. Then use tzinfo class to convert our datetime to UTC. All NTP communication uses Coordinated Universal Time (UTC), which is the same as Greenwich Mean Time. Use the () to get the current date and time. NTP uses the User Datagram Protocol (UDP) as its transport protocol. An NTP server must be accessible by the client switch. With this synchronization, you can correlate events to the time that system logs were created and the time that other time-specific events occur. NTP synchronizes timekeeping among a set of distributed time servers and clients.
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