Syslog

Syslog is a standard protocol used for transmitting event messages from networking devices such as routers, switches, firewalls, and servers to a centralized logging server called a Syslog server. Syslog messages contain important information about device activity, including error messages, system events, and security alerts. In this blog, we will discuss the features and benefits of Syslog, including facilities and levels, how to configure Syslog on Cisco devices, and well-known tools used for Syslog analysis.

What is Syslog?

 

Syslog is a standard protocol that allows network devices to send event messages to a Syslog server. These messages contain important information about device activity, including system events, error messages, and security alerts. Syslog messages are sent over UDP or TCP protocols, depending on the configuration. Syslog is widely used in enterprise environments for centralized logging and analysis of network activity.

How to configure Syslog on Cisco devices?

To configure Syslog on Cisco devices, follow these steps:

Enable Syslog on the device by using the "logging" command.
Specify the destination of the Syslog messages by using the "logging host" command.
Specify the logging level for the messages by using the "logging trap" command.
Configure the Syslog facility to be used by using the "logging facility" command.

Here is an example of configuring Syslog on a Cisco device:

logging enable

logging host 192.168.1.100

logging trap informational

logging facility local6

This configuration enables Syslog, sets the destination of the Syslog messages to IP address 192.168.1.100, sets the logging level to informational, and sets the Syslog facility to local6.

Syslog Flow:

The following diagram shows the flow of Syslog messages from a device to a Syslog server:

 

When a device generates a Syslog message, it sends it to the configured Syslog server using UDP or TCP protocols. The Syslog server receives the messages and stores them in a file or database for further analysis.

Syslog Facilities and Levels:

Syslog messages are categorized into facilities and levels. Facilities are used to classify messages based on their source, while levels are used to classify messages based on their severity.

There are eight Syslog facilities, including:

• Kernel messages
• User-level messages
• Mail system messages
• System daemons
• Security/authorization messages
• Messages generated internally by Syslog
• Line printer messages
• Network news subsystem

There are eight Syslog levels, including:

• Emergency: system is unusable
• Alert: action must be taken immediately
• Critical: critical conditions
• Error: error conditions
• Warning: warning conditions
• Notice: normal but significant condition
• Informational: informational messages
• Debug: debug-level messages

Use Cases of Syslog:

Syslog is used in enterprise environments for centralized logging and analysis of network activity. Some use cases of Syslog include:

Security monitoring: Syslog messages can be used to detect security breaches and suspicious activity on the network.
Troubleshooting: Syslog messages can be used to identify and resolve issues with network devices.
Performance monitoring: Syslog messages can be used to monitor network performance and identify bottlenecks.
Compliance auditing: Syslog messages can be used to ensure compliance with industry regulations and internal policies.

Well-known Tools for Syslog:

There are several well-known tools used for Syslog analysis, including:

Splunk: a commercial log management platform that allows you to search, monitor,and analyze Syslog messages in real-time.

ELK Stack: a free and open-source log management platform that allows you to collect, store, and analyze Syslog messages.

Nagios Log Server: a commercial log management platform that allows you to collect, analyze, and alert on Syslog messages.

Conclusion

Syslog is a powerful protocol used for transmitting event messages from networking devices to a centralized logging server. Syslog messages contain important information about device activity, including error messages, system events, and security alerts. Facilities and levels are used to classify messages based on their source and severity. Syslog is widely used in enterprise environments for centralized logging and analysis of network activity. Well-known tools such as Graylog, Splunk, ELK Stack, Nagios Log Server, and Kiwi Syslog Server can be used to collect, store, and analyze Syslog messages.