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Cisco IOS Software Configuration Guide for Cisco Aironet Access Points
OL-30644-01
Chapter 5 Administrating the Access Point
Managing the System Time and Date
Understanding Simple Network Time Protocol
Simple Network Time Protocol (SNTP) is a simplified, client-only version of NTP. SNTP can only
receive the time from NTP servers; it cannot be used to provide time services to other systems. SNTP
typically provides time within 100 milliseconds of the accurate time, but it does not provide the complex
filtering and statistical mechanisms of NTP.
You can configure SNTP to request and accept packets from configured servers or to accept NTP
broadcast packets from any source. When multiple sources are sending NTP packets, the server with the
best stratum is selected. Click this URL for more information on NTP and strata:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_configuration_guide_chapter0918
6a00800ca66f.html#1001131
If multiple servers are at the same stratum, a configured server is preferred over a broadcast server. If
multiple servers pass both tests, the first one to send a time packet is selected. SNTP will only choose a
new server if it stops receiving packets from the currently selected server, or if a better server (according
to the above criteria) is discovered.
Configuring SNTP
SNTP is disabled by default. To enable SNTP on the access point, use one or both the commands listed
in Table 5-4 in the global configuration mode.
Enter the sntp server command once for each NTP server. The NTP servers must be configured to
respond to the SNTP messages from the access point.
If you enter both the sntp server command and the sntp broadcast client command, the access point
will accept time from a broadcast server but prefers time from a configured server, assuming the strata
are equal. To display information about SNTP, use the show sntp EXEC command.
Configuring Time and Date Manually
If no other source of time is available, you can manually configure the time and date after the system is
restarted. The time remains accurate until the next system restart. We recommend that you use manual
configuration only as a last resort. If you have an outside source to which the wireless device can
synchronize, you do not need to manually set the system clock.
This section contains this configuration information:
• Setting the System Clock, page 5-31
• Displaying the Time and Date Configuration, page 5-32
Table 5-4 SNTP Commands
Command Purpose
sntp server {address | hostname}
[version number]
Configures SNTP to request NTP packets from an
NTP server.
sntp broadcast client Configures SNTP to accept NTP packets from any
NTP broadcast server.