This Simple Explanation from CCNA Official Guide Book is easy to understand System Message Format of Cisco Router. Let ‘s Start.
Let’s examine one of the messages from our Cisco router to examine the default message format:
*Dec 18 17:10:15.079: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to down
Notice that by default on this particular device, we see the following:
A timestamp: *Dec 18 17:10:15.079
The facility on the router that generated the message: %LINEPROTO
The severity level: 5
A mnemonic for the message: UPDOWN
The description of the message: Line protocol on Interface FastEthernet0/0, changed state to down
Turn off timestamps and turn on sequence numbers
R1(config)# no service service timestamps
000011: %SYS-5-CONFIG_I: Configured from console by console
The message format now features the following:
Sequence number: 000011
Severity level: 5
Description: Configured from console by console
One of the most important ingredients in the system message on a Cisco device is the severity level. This is because we can use severity levels to easily control which messages are sent to which logging destinations.
Level 0 > Emergency > The system may be unusable.
Level 1 > Alert > Immediate action may be required.
Level 2 > Critical > A critical event took place.
Level 3 > Errot > The router experienced an error.
Level 4 > Warning > A confition might warrant attention.
Level 5 > Notification > A normal but significant confition occurred.
Level 6 > Informational > A normal event occurred.
Level 7 > Debugging > The output is a result of a debug command.
Levels 5 through 7 are for less important events.