Cisco UCS

SEL log reading (CISCO Switches)

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Cisco SEL (System Event Log) analysis is a critical task for network administrators and engineers to identify and troubleshoot issues in Cisco networking devices. The SEL captures various system events and messages, providing valuable insights into the health, performance, and security of Cisco devices. In this comprehensive guide, we’ll explore the importance of SEL analysis, the structure of SEL messages, common SEL entries, and examples of SEL log analysis to demonstrate how it can be performed effectively.

1. Importance of Cisco SEL Analysis:

Cisco devices, such as routers, switches, and servers, generate SEL messages to record events related to hardware, software, and system operations. SEL analysis is essential for the following reasons:

  • Troubleshooting: SEL messages can help identify the root cause of network issues, hardware failures, or abnormal behaviors in Cisco devices.
  • Monitoring: Monitoring SEL logs enables proactive maintenance, detecting potential hardware failures or system events that may affect network performance.
  • Security: SEL logs can provide evidence of unauthorized access attempts or security breaches in Cisco devices.
  • Compliance: Many industry regulations require logging and monitoring of critical events, making SEL analysis crucial for compliance purposes.

2. Structure of Cisco SEL Messages:

SEL messages are stored in the device’s SEL log, usually in non-volatile memory (NVRAM). The SEL log follows the IPMI (Intelligent Platform Management Interface) v2.0 standard and consists of timestamped records, each containing various fields, including:

  • Record ID: A unique identifier for the SEL record.
  • Timestamp: The date and time when the event occurred.
  • Sensor Type: Identifies the source of the event, such as temperature, voltage, fan, power supply, etc.
  • Event Type: Describes the nature of the event, such as threshold crossing, sensor-specific, or OEM-specific events.
  • Event Data: Specific data related to the event, such as sensor values, device status, or error codes.
  • Sensor ID: Identifies the specific sensor generating the event.
  • Entity ID: Identifies the device or component that the sensor belongs to.

3. Common SEL Entries and Examples:

a) Temperature Threshold Crossing:

ID | TimeStamp                | Sensor Type       | Event Type              | Event Data         | Sensor ID | Entity ID
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1  | 2023-07-20T09:32:15.123Z | Temperature       | Threshold Crossed Upper | Temperature = 80C  | 7Fh       | System Board

Explanation: In this example, the SEL entry indicates that the temperature sensor on the system board (Entity ID) has crossed the upper threshold of 80°C.

b) Power Supply Status Change:

ID | TimeStamp                | Sensor Type       | Event Type              | Event Data                 | Sensor ID | Entity ID
---------------------------------------------------------------------------------------------------------------------------
2  | 2023-07-20T09:45:22.789Z | Power Supply      | State Deasserted        | Power Supply Status = Off  | 01h       | Power Supply 1

Explanation: This SEL entry indicates that Power Supply 1 (Entity ID) has been deasserted, and its status is now “Off.”

c) Fan Speed Threshold Crossing:

ID | TimeStamp                | Sensor Type       | Event Type              | Event Data                  | Sensor ID | Entity ID
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3  | 2023-07-20T10:15:55.456Z | Fan               | Threshold Crossed Lower | Fan Speed = 1200 RPM        | 04h       | Fan Module 2

Explanation: The SEL entry shows that the fan speed (Sensor ID) in Fan Module 2 (Entity ID) has crossed the lower threshold of 1200 RPM.

d) Security Event: Login Attempt Failure

ID | TimeStamp                | Sensor Type       | Event Type              | Event Data         | Sensor ID | Entity ID
-------------------------------------------------------------------------------------------------------------------
4  | 2023-07-20T10:30:08.987Z | Security Audit    | Login Failed            | User = admin       | 70h       | Management Controller

Explanation: This SEL entry indicates a security event where a login attempt by the user “admin” (Event Data) to the Management Controller (Entity ID) has failed.

4. Analyzing SEL Logs:

  • Identify Critical Events: Analyze SEL logs regularly to identify critical events or alarms, such as temperature threshold crossings, power supply failures, or fan speed anomalies.
  • Cross-Reference with Other Logs: Correlate SEL logs with other system logs, such as syslog or SNMP traps, to get a comprehensive view of the system’s behavior and diagnose issues effectively.
  • Automated Monitoring: Use SNMP-based monitoring tools or SIEM (Security Information and Event Management) solutions to automate SEL log analysis and receive real-time alerts for critical events.
  • Track Hardware Changes: Monitor SEL logs during hardware upgrades or replacements to ensure new components are functioning correctly and detect any compatibility issues.
  • Regular Maintenance: Regularly clear SEL logs and archive old logs to maintain optimal system performance and prevent storage overflow.

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