Configures a Network TIme Protocol (NTP) server for use by the local
NTP client in synchronizing the system clock.
Privilege
Security Administrator, Administrator
Mode
Exec > Global Configuration > NTP Configuration
configure > ntp
Entering the above command sequence results in the following prompt:
[local]host_name(config-ntp)#
Syntax
server ip_address [ prefer ] [ version number ] [ minpoll poll_period ] [ maxpoll poll_period ]
no server ip_address
no
Indicates the server specified is to be removed from the list of NTP
servers for clock synchronization.
ip_address
Specifies the IP address of the NTP server to be used for clock
synchronization in IPv4 dotted-decimal or IPv6 colon-separated-hexadecimal
notation.
NTP should be configured for at least
three external NTP servers. With three or more servers, outlyers
and broken or misconfigured servers can be detected and excluded. Generally,
the more servers the better (within reason).
prefer
Indicates the NTP server specified to be the preferred server. Only
one server can be set to preferred. The preferred server is the first one
contacted for clock synchronization.
 Important |
Use of the
prefer keyword is
not recommended.
|
 Important |
Do
not change the
version,
minpoll or
maxpoll keyword settings unless instructed to do so by Cisco
TAC.
|
version
number
Specifies the network timing protocol version to use for server
communications as an integer from 1 to 4. Default: 4 (RFC 5905)
minpoll
poll_period
Specifies the minimum polling interval (in seconds) for NTP messages
as a power of 2.
poll_period is the exponent (power of)
expressed as an integer from 6 through 17. For example, if you specify the
number 6, the value is 2^6 and the resultant poll period is 64 seconds.
Default: 6
maxpoll
poll_period
Specifies the maximum polling interval (in seconds) for NTP messages
as a power of 2.
poll_period is the exponent (power of)
expressed as an integer from 6 through 17. For example, if you specify the
number 10, the value is 2^10 and the resultant poll period is 1024 seconds.
Default: 10
Usage Guidelines
Configure the NTP servers in response to network changes.
Refer to the
System Administration Guide for important information on
configuring NTP servers with local sources, and using a load balancer to
communicate with external NTP servers.
 Important |
Adding, removing, or modifying an NTP server configuration entry
causes the NTP client to restart itself and resynchronize with all configured
NTP servers.
|
Examples
The following command adds the NTP server with address
10.2.3.4 to the list of NTP servers.
server 10.2.3.4