Configuring Network Time Protocol Support - Cisco ASR 5500 Administration Manual

Configuring Network Time Protocol Support

Configuring Network Time Protocol Support
This section provides information and instructions for configuring the system to enable the use of the Network
Time Protocol (NTP).
Important
Many of the services offered by the ASR 5x00 platform require accurate timekeeping derived through NTP.
If the time reference(s) used by StarOS are not accurate, the services may be unreliable. For this reason it
should be assumed that normal system operation requires that NTP be configured.
The system uses NTP to synchronize internal clocks on the chassis to external time sources (typically GPS
NTP sources, or other Stratum 2 or 3 servers, switches or routers).
By default, NTP is not enabled externally and should be configured when the system is initially installed.
When enabled, the active MIO/UMIO will synchronize with external sources. If not enabled, the active
MIO/UMIO will use its local clock as a time source. In the event of an NTP server or network outage, an
already running MIO/UMIO will continue to use NTP to maintain time accuracy, but in a holdover mode.
All cards with CPUs synchronize to the active MIO/UMIO internally. This occurs even if an external NTP
server is not configured. In the event of a MIO/UMIO switchover, all other cards will start synchronizing
with the newly active MIO/UMIO automatically.
The system should have:
• NTP enabled.
• NTP configured for use in the local context only. Use of other contexts (which can be specified in the
• NTP configured for at least three external NTP servers. With three or more servers, outlyers and broken
Important
Important
Use the following example to configure the necessary NTP association parameters:
configure
ntp
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Configure the system clock and time zone prior to implementing NTP support. This greatly reduces the
time period that must be corrected by the NTP server.
enable configurable) will cause issues.
or misconfigured servers can be detected and excluded. Generally, the more servers the better (within
reason).
Do not configure any external NTP servers using the prefer keyword. The NTP clock selection algorithms
already have the built-in ability to pick the best server. Use of prefer usually results in a poorer choice
than NTP can determine for itself.
Do not change the maxpoll, minpoll, or version keyword settings unless instructed to do so by Cisco
TAC.
enable
server ip_address1
server ip_address2
System Settings