Cisco IOS Cookbook, 2nd Edition

Time-Stamping Router Logs

Problem

You want the router to record the time along with log and debug messages.

Solution

The service timestamp global configuration command enables timestamps on debug and logging messages. Use the log keyword to turn on time-stamping of log messages:

Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#service timestamps log datetime localtime
Router(config)#end
Router#

The command to turn on timestamps for debug messages is similar, but uses the debug keyword:

Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#service timestamps debug datetime localtime
Router(config)#end
Router#

Discussion

By default, Cisco routers create log and debug messages without any form of timestamp. These messages are useful if the administrator is watching them in real time. However, it impossible to look at the logs later and understand what exactly happened when. This example illustrates the problem:

%SYS-5-CONFIG_I: Configured from console on vty1 (172.25.1.1)
%CLEAR-5-COUNTERS: Clear counter on all interfaces on vty1 (172.25.1.1)
%OSPF-5-ADJCHG: Process 55, Nbr 172.25.25.6 on FastEthernet0/0.1 from FULL to DOWN

You can’t tell when the router configuration was changed or when the OSPF neighbor state change. And, in particular, you can’t tell if the configuration change caused the OSPF problem. Having accurately time-stamped log messages makes troubleshooting and problem determination ...