Cisco Router Configuration, Second Edition

Basic Time Control

The Cisco IOS allows a device to track the current time and date using a system clock. The system clock starts when the device powers on and can distribute the time to a variety of internal systems, such as recording the time and date for configuration changes, displaying the time of buffered log messages, and sending the time and date in SNMP messages. On Cisco 7000 routers only, the system clock time is set in hardware. On other models, the system clock is set by default to midnight on March 1, 1993.

After it is set, the system clock determines whether the date and time are from a reliable source. If the time source is reliable, it is redistributed to other processes in the IOS; otherwise, the time is available only for ...