PRTG Manual: Syslog Receiver Sensor

The Syslog Receiver sensor receives and analyzes Syslog messages.

The sensor can show the following:

  • Number of received Syslog messages per second
  • Number of messages categorized as "warning" per second
  • Number of messages categorized as "error" per second
  • Number of dropped packets per second on the syslog port
Syslog Receiver Sensor

Syslog Receiver Sensor

Sensor in Other Languages

Dutch: Syslog ontvanger, French: Récepteur Syslog, German: Syslog-Empfänger, Japanese: Syslog レシーバー, Portuguese: Destinatário de syslog, Russian: Приемник Syslog, Simplified Chinese: 系统日志接收程序, Spanish: Receptor Syslog

Remarks

  • This sensor can have a high impact on the performance of your monitoring system. Use it with care. We recommend that you use no more than 50 sensors of this sensor type on each probe.
  • You cannot use this sensor in cluster mode. You can only set it up on a local probe or a remote probe but not on a cluster probe.
  • If you do not add the sensor to a probe device but to another device in PRTG, be careful with the configuration: Ensure that the IP address or Domain Name System (DNS) name of the parent device matches the proper sender. For example, if you want to receive messages from a storage area network (SAN), you might have to add a device to PRTG using the IP address of a specific array member that sends the messages. Providing a DNS name that points to the IP address of a whole group might not work for SANs.
  • With the available filter options, you can individually define which types of messages the sensor will consider for monitoring, and which messages it will categorize as warning or error messages. Depending on the filters, received messages are counted in the respective channels.
  • Add this sensor to the probe device to receive all messages of the system running the probe.
  • Add this sensor to a specific device to directly receive all messages from this device. This makes this sensor faster than just using source filters.
  • For a general introduction to the receiver's configuration, see section Monitoring Syslogs and SNMP Traps.
  • You can use specific placeholders in email notification templates to see the messages when you receive an email notification. See the Knowledge Base: What placeholders can I use with PRTG?
  • Sensor states of this sensor persist for one scanning interval only. After showing a Warning status or a Down status, and if there is no warning or error message in the following scanning interval, the sensor will show an Up status again. For a workaround, see the Knowledge Base: How can I configure sensors using speed limits to keep the status for more than one interval?

icon-prtg-on-demandYou cannot add this sensor to the Hosted Probe of a PRTG hosted by Paessler instance. If you want to use this sensor, add it to a remote probe device.

Add Sensor

The Add Sensor dialog appears when you manually add a new sensor to a device. It only shows the setting fields that are required for creating the sensor. Therefore, you will not see all setting fields in this dialog. You can change (nearly) all settings in the sensor's Settings tab later.

Sensor Settings

On the details page of a sensor, click the Settings tab to change its settings.

icon-i-roundUsually, a sensor connects to the IP Address or DNS Name of the parent device on which you created the sensor. See the Device Settings for details. For some sensors, you can explicitly define the monitoring target in the sensor settings. See below for details on available settings.

Basic Sensor Settings

Sensor Name

Enter a meaningful name to identify the sensor. By default, PRTG shows this name in the device tree, as well as in alarms, logs, notifications, reports, maps, libraries, and tickets.

Parent Tags

Shows Tags that this sensor inherits from its parent device, group, and probe. This setting is shown for your information only and cannot be changed here.

Tags

Enter one or more Tags, separated by spaces or commas. You can use tags to group sensors and use tag–filtered views later on. Tags are not case sensitive. We recommend that you use the default value.

There are default tags that are automatically predefined in a sensor's settings when you add a sensor. See section Default Tags below.

You can add additional tags to the sensor if you like. Other tags are automatically inherited from objects further up in the device tree. These are visible above as Parent Tags.

icon-i-roundIt is not possible to enter tags with a leading plus (+) or minus (-) sign, nor tags with parentheses (()) or angle brackets (<>).

Priority

Select a priority for the sensor. This setting determines where the sensor is placed in sensor lists. A sensor with a top priority is at the top of a list. Choose from one star (low priority) to five stars (top priority).

Default Tags

syslogsensor

Syslog Specific

Listen on Port

Enter the number of the port on which the sensor listens for Syslog messages. Default port is 514. Enter an integer value. We recommend that you use the default value.

Purge Messages After

Define how long PRTG stores received Syslog messages for analysis. Select a period of time from the dropdown list.

Filter

Include Filter

Define if you want to filter Syslog messages. If you leave this field empty or use the keyword any, the sensor will process all data. To only include specific types of messages, define filters using a special syntax.

icon-book-arrowsFor more information, see section Filter Rules.

Exclude Filter

Define which types of Syslog messages the sensor will discard and not process. To exclude specific types of messages, define filters using a special syntax.

icon-book-arrowsFor more information, see section Filter Rules.

Warning Filter

Define which types of Syslog messages count for the Warnings channel. To categorize received messages as warning messages, define filters using a special syntax.

icon-book-arrowsFor more information, see section Filter Rules.

icon-i-roundMessages are collected until a scanning interval ends. As long as the scanning interval is running, no status change will happen. By default, the sensor will change to a Warning status after a scanning interval has finished and there has at least been one warning message (and no error message) during this interval. The sensor will show a Warning at least until the succeeding scanning interval has finished. If the sensor does not receive any warning or error message in this scanning interval, its status will change to Up again with the start of the next scanning interval.

Error Filter

Define which types of Syslog messages will count for the Errors channel. To categorize received messages as error messages, define filters using a special syntax.

icon-book-arrowsFor more information, see section Filter Rules.

icon-i-roundMessages are collected until a scanning interval ends. As long as the scanning interval is running, no status change will happen. By default, the sensor will change to a Down status after a scanning interval has finished and there has at least been one error message during this interval. The sensor will show a Down status at least until the succeeding scanning interval has finished. If the sensor does not receive any warning or error message in this scanning interval, its status will change to Up again with the start of the next scanning interval.

Sensor Display

Primary Channel

Select a channel from the list to define it as the primary channel. In the device tree, the last value of the primary channel is always displayed below the sensor's name. The available options depend on what channels are available for this sensor.

icon-i-roundYou can set a different primary channel later by clicking the pin symbol of a channel on the sensor's Overview tab.

Graph Type

Define how different channels will be shown for this sensor.

  • Show channels independently (default): Show a graph for each channel.
  • Stack channels on top of each other: Stack channels on top of each other to create a multi-channel graph. This will generate a graph that visualizes the different components of your total traffic.
    icon-i-roundThis option cannot be used in combination with manual Vertical Axis Scaling (available in the Sensor Channel Settings settings).

Stack Unit

This field is only visible if you enable Stack channels on top of each other above. Select a unit from the list. All channels with this unit will be stacked on top of each other. By default, you cannot exclude single channels from stacking if they use the selected unit. However, there is an advanced procedure to do so.

Inherited Settings

By default, all of the following settings are inherited from objects that are higher in the hierarchy and should be changed there if necessary. Often, best practice is to change them centrally in the Root group's settings. For more information, see section Inheritance of Settings. To change a setting for this object only, disable inheritance by clicking the button next to inherit from under the corresponding setting name. You will then see the options described below.

Scanning Interval

Click inherited_settings_button to interrupt the inheritance. See section Inheritance of Settings for more information.

Scanning Interval

Select a scanning interval (seconds, minutes, or hours). The scanning interval determines the amount of time that the sensor waits between two scans. You can change the available intervals in the system administration on PRTG on premises installations.

If a Sensor Query Fails

Define the number of scanning intervals that the sensor has time to reach and check a device again in case a sensor query fails. Depending on the option that you select, the sensor can try to reach and check a device again several times before the sensor will show a Down status. This can avoid false alarms if the monitored device only has temporary issues. For previous scanning intervals with failed requests, the sensor will show a Warning status. Choose from:

  • Set sensor to down immediately: Set the sensor to a Down status immediately after the first failed request.
  • Set sensor to warning for 1 interval, then set to down (recommended): Set the sensor to a Warning status after the first failed request. If the following request also fails, the sensor will show an error.
  • Set sensor to warning for 2 intervals, then set to down: Set the sensor to a Down status only after three consecutively failed requests.
  • Set sensor to warning for 3 intervals, then set to down: Set the sensor to a Down status only after four consecutively failed requests.
  • Set sensor to warning for 4 intervals, then set to down: Set the sensor to a Down status only after five consecutively failed requests.
  • Set sensor to warning for 5 intervals, then set to down: Set the sensor to a Down status only after six consecutively failed requests.

icon-i-roundSensors that monitor via Windows Management Instrumentation (WMI) always wait at least one scanning interval before they show a Down status. It is not possible to immediately set a WMI sensor to a Down status, so the first option will not apply to these sensors. All other options can apply.

icon-i-roundIf you define error limits for a sensor's channels, the sensor will immediately show a Down status. No "wait" option will apply.

icon-i-roundIf a channel uses lookup values, the sensor will immediately show a Down status. No "wait" options will apply.

Schedules, Dependencies, and Maintenance Window

icon-i-roundYou cannot interrupt the inheritance for schedules, dependencies, and maintenance windows. The corresponding settings from the parent objects will always be active. However, you can define additional settings here. They will be active at the same time as the parent objects' settings.

Schedule

Select a schedule from the list. Schedules can be used to monitor for a certain time span (days or hours) every week.

icon-book-arrowsYou can create schedules, edit schedules, or pause monitoring for a specific time span. For more information, see section Account Settings—Schedules.

icon-i-roundSchedules are generally inherited. New schedules will be added to existing schedules, so all schedules are active at the same time.

Maintenance Window

Specify if you want to set up a one-time maintenance window. During a maintenance window, the current sensor and all child objects will not be monitored. They will be in a Paused status instead. Choose between:

  • Not set (monitor continuously): No maintenance window will be set and monitoring will always be active.
  • Set up a one-time maintenance window: Pause monitoring within a maintenance window. You can define a time span for a monitoring pause below and change it even for a currently running maintenance window.

icon-i-roundTo terminate a current maintenance window before the defined end date, change the time entry in Maintenance Ends to a date in the past.

Maintenance Begins

This field is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the start date and time of the maintenance window.

Maintenance Ends

This field is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the start date and time of the maintenance window.

Dependency Type

Define a dependency type. You can use dependencies to pause monitoring for an object depending on the status of another object. You can choose from:

  • Use parent: Use the dependency type of the parent device.
  • Select a sensor: Use the dependency type of the parent device. Additionally, pause the current sensor if another specific sensor is in a Down status or in a Paused status caused by another dependency. Select below.
  • Master sensor for parent: Make this sensor the master object for its parent device. The sensor will influence the behavior of its parent device: If the sensor is in a Down status, the device will be paused. For example, it is a good idea to make a Ping sensor the master object for its parent device to pause monitoring for all other sensors on the device in case the device cannot even be pinged. Additionally, the sensor will be paused if the parent group is paused by another dependency.

icon-i-roundTo test your dependencies, select Simulate Error Status from the context menu of an object that other objects depend on. A few seconds later, all dependent objects will be paused. You can check all dependencies in your PRTG installation by selecting Devices | Dependencies from the main menu bar.

Dependency

This field is only visible if you enable Select a sensor above. Click the Search button and use the object selector to select a sensor on which the current sensor will depend.

Dependency Delay (Sec.)

This field is only visible if you enable Select a sensor above. Define a time span in seconds for dependency delay.

After the master sensor for this dependency comes back to an Up status, monitoring of the dependent objects will be additionally delayed by the defined time span. This can help avoid false alarms, for example, after a server restart, by giving systems more time for all services to start up. Enter an integer value.

icon-i-round-redThis setting is not available if you set this sensor to Use parent or to be the Master sensor for parent. In this case, define delays in the parent Device Settings or in its parent Group Settings.

Access Rights

Click inherited_settings_button to interrupt the inheritance. See section Inheritance of Settings for more information.

User Group Access

Define the user groups that will have access to the selected object. A table with user groups and types of access rights is shown. It contains all user groups from your setup. For each user group, you can choose from the following access rights:

  • Inherited: Use the access rights settings of the parent object.
  • None: Users in this group cannot see or edit the object. The object neither shows up in lists nor in the device tree. Exception: If a child object is visible to the user, the object is visible in the device tree but it cannot be accessed.
  • Read: Users in this group can see the object and review its monitoring results.
  • Write: Users in this group can see the object, review its monitoring results, and edit its settings. They cannot edit access rights settings.
  • Full: Users in this group can see the object, review its monitoring results, edit its settings, and edit access rights settings.

You can create new user groups in the System Administration—User Groups settings. To automatically set all objects further down in the hierarchy to inherit this object's access rights, set a check mark for the Revert children's access rights to inherited option.

icon-book-arrowsFor more details on access rights, see section User Access Rights.

Channel Unit Configuration

Click inherited_settings_button to interrupt the inheritance. See section Inheritance of Settings for more information.

Channel Unit Types

For each type of sensor channel, define the unit in which data is displayed. If defined on probe, group, or device level, these settings can be inherited to all sensors underneath. You can set units for the following channel types (if available):

  • Bandwidth
  • Memory
  • Disk
  • File
  • Custom

icon-i-roundCustom channel types can be set on sensor level only.

Debugging

Log Data to Disk

Define if the probe will write a logfile of the received data to the data folder (see Data Storage) to the disk for debugging purposes. Choose between:

  • Off (recommended): Do not write additional logfiles. Recommended for normal use cases.
  • On: Write logfiles for all data received.

icon-i-redUse with caution! When enabled, huge data files can be created. Use for a short time and for debugging purposes only.

Filter Rules for Syslog Messages

Filter rules are used for the include, exclude, warning, and error definition fields of the Syslog Receiver sensor. They are based on the following format:

field[filter]

You can use various filters suitable to your needs. Include and exclude filters define which messages should be monitored. Warning and error filters define how to categorize received messages. Provide these filters in the sensor settings as formulas. Formulas are fields that you can combine with boolean operators (AND, OR, NOT) and brackets.

Field

Parameter

Example

source[ip]

Enter an IP address where the messages come from. IP masks and ranges are also possible.

  • source[10.0.23.50]
  • source[10.0.23.10-50]
  • source[10.0.23.10/255]
     

facility[number]

Enter any number or range from 0 to 23 specifying the program type that sends the message.

  • facility[2]
  • facility[5-7]
  • facility[5] OR facility[6]
     

severity[number]

Enter any number or range from 0 (emergency) to 7 (debug) specifying the message type.

  • severity[4]
  • severity[1-3]
  • severity[1] AND severity[2]
     

hostname[text]

Enter any string that specifies the hostname of a device in the message.

  • hostname[www.example.com]
     

tag[text]

Enter any string that specifies the tag of a program or process in the message.

  • tag[su]
     

appname[text]

Enter any string that specifies the appname part of the message.

  • appname[myproc]
  • appname[demo] AND msgid[m42]
     

procid[text]

Enter any string that specifies the process identifier part of the message.

  • procid[1860]
     

msgid[text]

Enter any string that specifies the message identifier part of the message.

  • msgid[ID47]
     

message[parttext]

Enter any string that specifies the message part of the message. (Any substring will match. This value is case insensitive.)

  • message[Error]
     

data[id,param,value]

This checks the SD-ID block of the message's structured data for a parameter matching the given value.

data[parttext]

This checks if the given substring matches structured data as displayed in the corresponding table.

data[id,param]

This checks if the parameter exists in the given ID element.

icon-i-round-redString parameters (except the substring in message) have to exactly match the particular parts of the message. They are case sensitive!

Messages Tab: Review and Analyze Syslog Messages

PRTG stores received Syslog messages as common files in the data folder (see section Data Storage). To review and analyze all received messages, you can directly access the most recent data in a table list on the PRTG web interface. You can access this list via the sensor's Overview tab.

icon-i-roundReceived Syslog messages are only shown in the table on the Overview tab after an (automatic) page refresh following a sensor scan. The default value for auto refresh is 30 seconds.

For more details and further filter options, click the Messages tab of the Syslog Receiver sensor. You will see all received messages in a table list. On the top, you have display filter options to drill down into the data for specific events of your interest. The filters are the same as those available in the sensor settings, but you can define them without using formulas. Provide the desired parameters and PRTG automatically loads the filtered list.

icon-i-roundYou can automatically add a filter by clicking the content of a column.

Advanced Filter Settings

You can open advanced filter settings by clicking the gear icon in the Filter row. The Advanced Filter will appear in a popup window. In the text field, you can define a filter using the syntax as given in section Filter Rules for Syslog Messages.

If you provided filter parameters on the Messages tab, the advanced filter will already include them as a corresponding formula with the correct syntax. You can adjust this filter to your needs. You can also copy the automatically created and manually adjusted formula for usage in the filter fields of the sensor settings.

More

Knowledge Base: How can I configure sensors using speed limits to keep the status for more than one interval?

Knowledge Base: What placeholders can I use with PRTG?

Video Tutorial: Trap Receiver and Syslog Receiver

Edit Sensor Channels

To change display settings, spike filtering, and limits, switch to the sensor's Overview tab and click the gear icon of a specific channel. For detailed information, see section Sensor Channel Settings.

Notification Triggers

Click the Notification Triggers tab to change notification triggers. For detailed information, see section Sensor Notification Triggers Settings.

Others

For more general information about settings, see section Object Settings.

Sensor Settings Overview

For information about sensor settings, see the following sections: