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5.5 | |
Configure Services | |
| 5.5.9 | |
NTP |
NTP is designed to synchronize the time on
a network of machines. NTP runs over the User Datagram Protocol (UDP),
using port 123 as both the source and destination, which in turn runs
over IP. NTP Version 3, RFC 1305, is used to synchronize timekeeping
among a set of distributed time servers and clients. A set of nodes on
a network are identified and configured with NTP and the nodes form a
synchronization subnet, sometimes referred to as an overlay network.
While multiple masters (primary servers) may exist, there is no
requirement for an election protocol. A sample NTP topology is shown
in Figure  .
From the Services>NTP Page,
select Enabled for the Network Time Protocol (NTP) if the network uses
NTP If the network has a default time server, enter the server IP address or host name in the Time Server (optional) field. Cisco Aironet APs do not have a hardware-supported clock, and they cannot function as an NTP master clock to which peers synchronize themselves when an external NTP source is not available. These access points also have no hardware support for a calendar. As a result, the ntp update-calendar and the ntp master global configuration commands are not available. The example below shows how to
configure the AP to synchronize only to devices providing
authentication key 42 in the NTP packets of the device and to
configure the AP to synchronize its system clock with the clock of the
peer at IP address 172.16.22.44 using NTP version 2. The default settings are
shown in Figure
|
,
. To turn Network Time Protocol (NTP) off, select Disabled. When
NTP is enabled, an NTP Status field appears. This field indicates
whether NTP is synchronized or unsynchronized. Click Refresh to update
this status. 
.The command
syntax and descriptions are shown in Figures
and
. 
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