Cisco 3750G - Catalyst Integrated Wireless LAN Controller, Руководство по настройке

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Catalyst 3750 Switch Software Configuration Guide
OL-8550-02
Chapter 7 Administering the Switch
Managing the System Time and Date
Figure 7-1 shows a typical network example using NTP. Switch A is the NTP master, with Switches B,
C, and D configured in NTP server mode, in server association with Switch A. Switch E is configured
as an NTP peer to the upstream and downstream switches, Switch B and Switch F.
Figure 7-1 Typical NTP Network Configuration
If the network is isolated from the Internet, Cisco’s implementation of NTP allows a device to act as if
it is synchronized through NTP, when in fact it has learned the time by using other means. Other devices
then synchronize to that device through NTP.
When multiple sources of time are available, NTP is always considered to be more authoritative. NTP
time overrides the time set by any other method.
Several manufacturers include NTP software for their host systems, and a publicly available version for
systems running UNIX and its various derivatives is also available. This software allows host systems to
be time-synchronized as well.
Configuring NTP
The switch does not have a hardware-supported clock and cannot function as an NTP master clock to
which peers synchronize themselves when an external NTP source is not available. The switch also has
no hardware support for a calendar. As a result, the
ntp update-calendar and the ntp master global
configuration commands are not available.
Switch F
Switch A
Workstations
Workstations
Local
workgroup
servers
101349
Switch B
Switch E
Switch C Switch D