Information Hierarchy

When a large amount of information is generated, it is difficult to differentiate between information about normal operations and information about faults. Using information hierarchy, users can perform a rough analysis of information based on severity levels and screen out unwanted information.

Information is divided into eight severity levels, with 0 being the most severe and 7 the least severe. Descriptions of the severity levels are listed in Table 1.

**Table 1** Description of information severity levels
Value	Severity	Description
0	Emergencies	A fatal fault, such as an abnormal program or a memory error, occurs on the device. The system must restart.
1	Alert	A major fault occurs, such as the device memory threshold reaches the upper limit. The fault needs to be rectified immediately.
2	Critical	A critical fault occurs, such as the device memory usage falls below the lower threshold or BFD detects that a device is unreachable. The fault needs to be analyzed and rectified.
3	Error	A fault caused by an incorrect operation or wrong process occurs, such as an incorrect command, incorrect user password, or protocol error packets are detected. The fault needs to be rectified.
4	Warning	An abnormal situation occurs, such as a user disables a routing process, BFD detects packet loss, or protocol error packets are detected. The fault may cause service processing faults, requiring attention.
5	Notification	Key operations are performed to ensure normal operation of the device. For example, the shutdown command is executed, a neighbor is discovered, or the protocol state machine status changes.
6	Informational	Common operations are performed to ensure normal operation of the device. For example, a display command is executed.
7	Debugging	Common information is generated during normal operation of the device, which requires no attention.

When information filtering based on severity levels is enabled, only information with severity levels lower than or equal to the configured severity level threshold is output. For example, if the severity level threshold is set to 6, only information with severity levels 0 to 6 is output.