System Time Configuration - Cisco Catalyst 2000 Configuration Handbook

48 Cisco LAN Switching Configuration Handbook
NTP associations with other NTP peers can be protected through an encrypted au-
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thentication.
NTP version 3 is based on RFC 1305 and uses UDP port 123. You can find information
about public NTP servers and other NTP subjects at http://www.ntp.org/htdig/search.
html or http://www.eecis.udel.edu/~mills/database/rfc/rfc1769.txt.
Note Catalyst 4500 and 6500 series switches running native IOS switches can also be
configured as NTP authoritative time sources. For configuration information on these
devices, check out the Cisco Network Time Protocol: Best Practices White Paper at http:
//www.tinyurl.com/4r3ow or refer to Cisco Field Manual: Router Configuration by David
Hucaby and Steve McQuerry, Cisco Press, ISBN 1-58705-024-2.

System Time Configuration

You can set the system time using two different ways:
Manually
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Using the NTP
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For manual configuration, you set the time and date on the router along with the time
zone and whether to observe summer hours. With manual configuration, the router has
no way to preserve the time settings and cannot ensure that time remains accurate. NTP
is defined by RFC 1305 and provides a mechanism for the devices in the network to get
their time from an NTP server. With NTP, all the devices would be synchronized and
keep accurate time.
Setting the System Time Manually
Set the time zone:
1.
(global) clock timezone zone hrs-offset min-offset
The time zone is set to the abbreviated name zone (that is, EST, PST, CET). This
name is used only for display purposes and can be any common zone name. The
actual displayed time is defined by an offset in hours (hrs-offset) and minutes (min-
offset) from UTC.
(Optional) Configure daylight savings time (DST):
2.
(global) clock summer-time zone recurring [week day month hh:mm week day month
hh:mm [offset]]
(global) clock summer-time zone date [date month | month date] year hh:mm [date
month | month date] year hh:mm [offset]
If DST begins and ends on a certain day and week of a month, use the command
with the recurring keyword. To start and stop DST, you can give the week number