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Without precise time synchronization between all the various logging, management, and AAA
functions, time comparisons are not possible.
An NTP enabled network usually gets its time from an authoritative time source, such as a Cisco router,
radio clock, or an atomic clock attached to a timeserver. NTP then distributes this time across the
network. NTP is extremely efficient; no more than one packet per minute is necessary to synchronize
two machines to within a millisecond of one another. NTP runs over UDP, which in turn runs over IP.
For more information, refer to the following URL:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/12cgcr/fun_c/
fcprt3/fcgenral.htm
Locate an authoritative clock source. For example, you can use a Cisco router or an atomic clock that
is attached to a time server.
Specify the primary NTP server IP address and automatic calendar updates as shown below:
!
ntp update-calendar
ntp server 172.22.66.18 prefer
!
Verify that the clock is synchronized to the NTP server. Inspect the status and time association.
Clock sources are identified by their stratum levels. The following example shows a stratum level five
clock.
5300-NAS#show ntp status
Clock is synchronized, stratum 5, reference is 172.22.66.18
nominal freq is 250.0000 Hz, actual freq is 250.0000 Hz, precision is 2**24
reference time is BB944312.4451C9E7 (23:11:30.266 PDT Wed Sep 22 1999)
clock offset is 0.5343 msec, root delay is 13.26 msec
root dispersion is 18.02 msec, peer dispersion is 0.09 msec
5300-NAS#
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The following command identifies how often the NAS is polling and updating to the stratum clock.
An asterisk (*) next to the NTP server s IP address indicates successful synchronization with the
stratum clock.
5300-NAS#show ntp association
address ref clock st when poll reach delay offset disp
*~172.22.66.18 172.60.8.1 16 46 64 377 1.0 0.53 0.1
* master (synced), # master (unsynced), + selected, - candidate, ~ configured
5300-NAS#
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The Cisco IOS can send syslog messages to one or more element manager servers. Syslog messages are
then collected by a standard UNIX or NT type syslog daemon.
Syslog enables you to:
" Centrally log and analyze configuration events and system error messages such as interface status,
security alerts, environmental conditions, and CPU process overloads.
" Capture client debug output sessions in a real-time scenario.
" Reserve telnet sessions for making configurations changes and using show commands.
This prevents telnet sessions from getting cluttered up with debug output.
Figure 7-2 shows the Cisco IOS sending syslog data to an element manager. Syslog data either stays in
the Cisco IOS buffer or is pushed out and written to the element manager s hard disk.
S Iá á H D
Syslog data
Syslog unidirectional
Element manager
running syslog
deamon
Cisco IOS sending
syslog data
Internal view
Syslog messages
written to
hard disk
Cisco System s UNIX syslog format is compatible with 4.3 BSD UNIX.
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Enable debug timestamps and include the date, time, and milliseconds relative to the local time zone:
!
service timestamps debug datetime msec localtime show-timezone
service timestamps log datetime msec localtime show-timezone
!
Verify that console logging is disabled. If it is enabled, the NAS will intermittently freeze up as soon as
the console port is overloaded with log messages. See the field 1 flushes. Increments on this number
represents bad logging behavior.
5300-NAS#show logging
Syslog logging: enabled (0 messages dropped, 1 flushes, 0 overruns)
Console logging: level debugging, 1523 messages logged
Monitor logging: level debugging, 0 messages logged
Buffer logging: level debugging, 911 messages logged
Trap logging: level informational, 44 message lines logged
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5300-NAS(config)#no logging console
5300-NAS(config)#^Z
5300-NAS#show logging
Syslog logging: enabled (0 messages dropped, 1 flushes, 0 overruns)
Console logging: disabled
Monitor logging: level debugging, 0 messages logged
Buffer logging: level debugging, 912 messages logged
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