What is Syslog?

• Syslog Definition

  Syslog Definition

  System Logging Protocol facilitates the transfer of information from network devices to a central server, known as syslog server, in a particular message format. This logging protocol is a crucial part of network monitoring as it helps you track the overall health of network devices by simplifying log message management.
• How does syslog work?

  How does syslog work?

  Before we deep dive into Syslog, it’s important for you to understand syslog. Network devices leverage syslog protocol to transfer event messages to a logging server. These messages contain information such as timestamps, device ID and IP address, event severity rating, and event-specific information. This logging protocol leverages layered architecture for monitoring network devices. Most network devices, such as routers and switches, support this protocol for event logging.

  Let us understand how it works:

  Syslog messages are transferred using User Datagram Protocol (UDP) on port 514. However, there’s no guarantee of message acknowledgment and delivery on the receiver/server-side due to the connectionless nature of UDP. Some network devices use TCP 1468 for confirmed message delivery to overcome this issue. Unlike the SNMP protocol, polling of network devices is avoided here to maintain system simplicity and ease of use.

  This network-based logging protocol has three layers with unique capabilities:

  • Syslog content: Contains the actual information present in the event message
  • Syslog application: Performs message routing, generation, interpretation, and storage
  • Syslog transport: Transfers the messages via the network
• Syslog benefits

  Syslog benefits

  Some of the key benefits of logging are as follows:

  Improved network performance: Having a standardized and centralized system, such as syslog collector, simplifies log management for network devices. It helps you save time, speed up the log review process, and implement preventive troubleshooting.

  Security: You can set forward authentication events to the logging server, such as syslog server for Linux, on all the idle devices without the need to install and configure a monitoring agent separately. By doing so, you can ensure critical events related to network devices are stored away from the original server, which prevents attackers from deleting the breach information.

  Advanced application monitoring: Application monitoring using the monitoring tool can help you gain insights into how the application is running on a server, but this could be restricted to specific aspects such as high CPU utilization or increase in memory usage. However, unlike this, logged events on syslog server for Linux or Unix can provide more granular information and deep dive into many other issues such as errors due to a new database write or attempt to access a locked file.
• Syslog format and messages

  Syslog format and messages

  Syslog message format is specified by RFC 5424, the syslog protocol. It’s common for network devices and applications. Standard syslog format ensures faster communication between network devices and the logging server. A syslog message has the following components:

  Header: The header contains details such as version, timestamp, hostname, application, process ID, message ID, application, and priority.

  Structured data: It contains the data blocks in a specific “key=value” order as per syslog format.

  Message: According to syslog message format, you should encode messages in UTF-8 form. Syslog protocol uses a calculated priority value (PRI) for message categorization. PRI data is calculated based on two values: Facility and Severity. Facility value helps determine the source of the message on a particular machine. For example, the facility value of “1” refers to the Kernel-level message. In comparison, the Severity value indicates the importance or criticalness of the message through a numeric value between 0 to 7.

  • Emergency messages (severity value 0): System is unavailable for use.
  • Alert messages (severity value 1): Immediate action required for system stability. 
  • Critical messages (severity value 2): Severe system issues such as loss of primary ISP connection.
  • Error messages (severity value 3): System errors requiring attention in a given time frame.
  • Warning messages (severity value 4): System error might occur if appropriate action is not taken. 
  • Notification messages (severity value 5): System is stable, but a significant condition persists. Immediate action is usually not required. 
  • Informational messages (severity value 6): System reporting and measuring messages.
  • Debugging messages (severity value 7): Debugging apps-specific messages.

  Message priority is decided by combining the Facility and Severity values. Further, the log message cannot be greater than 1024 bytes, as per the syslog message format. In addition, the actual content of the message isn’t specified by the protocol.
• Syslog servers

  Syslog servers

  Syslog server, also known as the syslog collector or receiver, centrally stores the syslog messages and SNMP traps from various network devices. With centralized storage, you can easily search, filter, and view the syslog messages. Syslog server typically contains the following components:

  • Syslog Listener: It gathers the event data to allow the collector to start receiving messages over the network.
  • Database: Syslog collector generates a large volume of data. A good server usually has a large database for fast read/write operations.

  Syslog collectors offer an intelligent alerting feature designed to notify you about upcoming problems with log messages to prevent network downtime or failure. It can also trigger automated responses to messages, such as running scripts and forwarding syslog messages. Moreover, a quality syslog collector supports log data archiving to help you comply with information security standards such as SOX, PCI-DSS, and FISMA.

  Syslog supports all variants of Linux, Unix, and macOS. You can easily configure servers on these platforms, such as syslog server for Linux. However, Windows OS doesn’t provide native support for this logging protocol. You can still use third-party tools to collect event logs for Windows and transfer them to a syslog service. Most pre-packaged software available as a syslog server for Windows provides free third-party tools for transferring the Windows event logs to the syslog collector.

  Typically, the syslog server for Windows can perform all log management actions. It can also handle events from other operating systems, such as Linux. Users who need a secure and centralized event logging mechanism can consider the syslog server for Windows. A Windows event log contains components such as date, time, user, computer, event ID, source, and type. You can consider the event log as a subset of what might be tracked via a syslog. A syslog captures log details of multiple devices in a central location.
• Monitoring syslog log files

  Monitoring syslog log files

  Syslog monitoring is a passive approach for network management. You can use monitoring and alerting tools to set up automated responses for certain event messages, like running automated scripts and sending email alerts to administrators. This helps you accelerate the damage control process and improve application availability during peak business hours.

  Syslog protocol supports various devices, including network components like routers and switches, web servers, and various operating systems like Linux and macOS. You can manage complex networks with large data volumes easily using syslog monitoring tools. Moreover, these tools can auto-split the event messages to display the sender, message, severity, and facility details for detailed analysis.

  A logging server like syslog server for Linux is crucial for effective monitoring of log files. The monitoring software usually has a syslog listener to capture syslog data and a database to store messages. Advanced monitoring software can also provide support for message buffering and filtration during log management.