C-15
Cisco Intrusion Prevention System Sensor CLI Configuration Guide for IPS 7.2
OL-29168-01
Appendix C Troubleshooting
Time Sources and the Sensor
Time Sources and the Sensor
This section describes how to maintain accurate time on the sensor, and contains the following topics:
•
Time Sources and the Sensor, page C-15
•
Synchronizing IPS Clocks with Parent Device Clocks, page C-15
•
Verifying the Sensor is Synchronized with the NTP Server, page C-16
•
Correcting Time on the Sensor, page C-16

Time Sources and the Sensor

Note
We recommend that you use an NTP server to regulate time on your sensor. You can use authenticated
or unauthenticated NTP. For authenticated NTP, you must obtain the NTP server IP address, NTP server
key ID, and the key value from the NTP server. You can set up NTP during initialization or you can
configure NTP through the CLI, IDM, IME, or ASDM.
The sensor requires a reliable time source. All events (alerts) must have the correct UTC and local time
stamp, otherwise, you cannot correctly analyze the logs after an attack. When you initialize the sensor,
you set up the time zones and summertime settings. This section provides a summary of the various ways
to set the time on sensors.
The IPS Standalone Appliances
•
Use the clock set command to set the time. This is the default.
•
Configure the appliance to get its time from an NTP time synchronization source.
Note
The currently supported Cisco IPS appliances are the IPS 4345, IPS 4360, IPS 4510, and IPS 4520.
The ASA IPS Modules
•
The ASA 5500-X IPS SSP and ASA 5585-X IPS SSP automatically synchronize their clocks with
the clock in the adaptive security appliance in which they are installed. This is the default.
•
Configure them to get their time from an NTP time synchronization source, such as a Cisco ro uter
other than the parent router.
For More Information
For the procedure for configuring NTP, see Configuring NTP, page 3-42.

Synchronizing IPS Clocks with Parent Device Clocks

The ASA IPS modules (ASA 5500-X IPS SSP and ASA 5585-X IPS SSP) synchronize their clocks to
the parent chassis clock (switch, router, or adaptive security appliance) each time the IPS boots up and
any time the parent chassis clock is set. The IPS clock and parent chassis clock tend to drift apart over
time. The difference can be as much as several seconds per day. To avoid this problem, make sure that
both the IPS clock and the parent clock are synchronized to an external NTP server. If only the IPS clock
or only the parent chassis clock is synchronized to an NTP server, the time drift oc curs.