Cisco_Nexus_7000_Series_NX-OS_System_Man.pdf

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C H A P T E R Send document comments to [email protected] 3-1 Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 5.x OL-20635-03 3 Configuring NTP This chapter describes how to configure the Network Time Protocol (NTP) on Cisco NX-OS devices. This chapter includes the following sections: Information About NTP, page 3-1 Licensing Requirements for NTP, page 3-3 Prerequisites for NTP, page 3-3 Guidelines and Limitations, page 3-3 Default Settings, page 3-4 Configuring NTP, page 3-4 Verifying the NTP Configuration, page 3-17 Configuration Examples for NTP, page 3-18 Additional References, page 3-19 Feature History for NTP, page 3-20 Information About NTP This section includes the following topics: NTP Overview, page 3-1 NTP as Time Server, page 3-2 Distributing NTP Using CFS, page 3-2 Clock Manager, page 3-2 High Availability, page 3-3 Virtualization Support, page 3-3 NTP Overview The Network Time Protocol (NTP) synchronizes the time of day among a set of distributed time servers and clients so that you can correlate events when you receive system logs and other time-specific events from multiple network devices. NTP uses the User Datagram Protocol (UDP) as its transport protocol. All NTP communications use Coordinated Universal Time (UTC).
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Send document comments to [email protected] 3-2 Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 5.x OL-20635-03 Chapter 3 Configuring NTP Information About NTP An NTP server usually receives its time from an authoritative time source, such as a radio clock or an atomic clock attached to a time server, and then distributes this time across the network. NTP is extremely efficient; no more than one packet per minute is necessary to synchronize two machines to within a millisecond of each other. NTP uses a stratum to describe the distance between a network device and an authoritative time source: A stratum 1 time server is directly attached to an authoritative time source (such as a radio or atomic clock or a GPS time source). A stratum 2 NTP server receives its time through NTP from a stratum 1 time server. Before synchronizing, NTP compares the time reported by several network devices and does not synchronize with one that is significantly different, even if it is a stratum 1. Because Cisco NX-OS cannot connect to a radio or atomic clock and act as a stratum 1 server, we recommend that you use the public NTP servers available on the Internet. If the network is isolated from the Internet, Cisco NX-OS allows you to configure the time as though it were synchronized through NTP, even though it was not. Note You can create NTP peer relationships to designate the time-serving hosts that you want your network device to consider synchronizing with and to keep accurate time if a server failure occurs.
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  • Fall '19
  • NTP, Network Time Protocol

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