C H A P T E; Implementing Ntp; Prerequisites For Implementing Ntp On Cisco Ios Xr Software; Information About Implementing Ntp - Cisco NCS 5000 Series Manual

Implementing NTP

Network Time Protocol (NTP) is a protocol designed to time-synchronize devices within a network.
Cisco IOS XR software implements NTPv4. NTPv4 retains backwards compatibility with the older versions
of NTP, including NTPv3 and NTPv2 but excluding NTPv1, which has been discontinued due to security
vulnerabilities.
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Prerequisites for Implementing NTP on Cisco IOS XR Software

You must be in a user group associated with a task group that includes the proper task IDs. The command
reference guides include the task IDs required for each command. If you suspect user group assignment is
preventing you from using a command, contact your AAA administrator for assistance.

Information About Implementing NTP

NTP synchronizes timekeeping among a set of distributed time servers and clients. This synchronization
allows events to be correlated when system logs are created and other time-specific events occur.
NTP uses the User Datagram Protocol (UDP) as its transport protocol. All NTP communication uses
Coordinated Universal Time (UTC). An NTP network usually receives its time from an authoritative time
source, such as a radio clock or an atomic clock attached to a time server. NTP 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 the concept of a "stratum" to describe how many NTP "hops" away a machine is from an authoritative
time source. A "stratum 1" time server typically has an authoritative time source (such as a radio or atomic
clock, or a GPS time source) directly attached, a "stratum 2" time server receives its time via NTP from a
"stratum 1" time server, and so on.
Prerequisites for Implementing NTP on Cisco IOS XR Software, page 145
Information About Implementing NTP, page 145
Configuration Examples for Implementing NTP, page 164
Configuring NTP server inside VRF interface, page 166
Additional References, page 168
System Management Configuration Guide for Cisco NCS 5000 Series Routers, IOS XR Release 6.2.x
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