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PRTG Manual: Syslog Receiver Sensor

The Syslog Receiver sensor receives and analyzes Syslog messages.

Syslog Receiver Sensor

For a detailed list and descriptions of the channels that this sensor can show, see section Channel List.

Sensor in Other Languages

Dutch: Syslog ontvanger
French: Récepteur Syslog
German: Syslog-Empfänger
Japanese: Syslog レシーバー
Portuguese: Receptor de Syslog
Russian: Приемник Syslog
Simplified Chinese: Syslog 接收程序
Spanish: Receptor de Syslog

Remarks

Consider the following remarks and requirements for this sensor:

Remark	Description
Performance impact	This sensor has a very high performance impact. We recommend that you use no more than 50 of this sensor on each probe.
UDP	This sensor only supports the User Datagram Protocol (UDP).
Cluster probe	This sensor does not support cluster probes. You can only set it up on local probes or remote probes.
IPv6	This sensor supports IPv6.
Probe device	Add this sensor to the probe device to receive all messages of the remote probe system. If you add the sensor to a device other than a probe device, the IP address or Domain Name System (DNS) name of the parent device must match the proper sender. For example, if you want to receive messages from a storage area network (SAN), you might need to add a device with 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.
Filter options	You can use the filter options to define which types of messages the sensor considers for monitoring, and which messages it categorizes as warnings or errors.
Specific device	Add this sensor to a specific device to directly receive all messages from this device. This is faster than using source filters.
Placeholders	You can use placeholders in email notification templates to see messages when you receive email notifications.
Sensor states	The sensor states of this sensor persist for one scanning interval only. After showing the Warning or the Down status, and if there is no warning or error message in the next scanning interval, the sensor shows the Up status again. For more information on a workaround, see the Knowledge Base: How can I configure sensors using speed limits to keep the status for more than one interval?
Hosted probe	You cannot add this sensor to the hosted probe of a PRTG Hosted Monitor instance. If you want to use this sensor, add it to a remote probe device.

Basic Sensor Settings

The sensor has the following default tags that are automatically predefined in the sensor's settings when you add the sensor:

syslogsensor

For more information about basic sensor settings, see section Sensor Settings.

Syslog Specific

Setting	Description
Port	Enter the number of the port on which the sensor listens for Syslog messages. The default port is 514. Enter an integer. 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.

Setting

Description

Port

Enter the number of the port on which the sensor listens for Syslog messages. The default port is 514. Enter an integer.

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

For more information, see section Filter Rules.

Filter

Setting	Description
Include Filter	Define if you want to filter Syslog messages. If you leave this field empty or use the keyword any, the sensor processes all data. To only include specific types of messages, define filters using a special syntax.
Exclude Filter	Define which types of Syslog messages the sensor discards and does not process. To exclude specific types of messages, define filters using a special syntax.
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. The sensor collects messages until a scanning interval ends. As long as the scanning interval is running, the sensor does not change its status. By default, the sensor changes to the Warning status after a scanning interval finishes and there was at least one warning message (and no error message) during this scanning interval. The sensor shows the Warning at least until the succeeding scanning interval finishes. If the sensor does not receive any warning or error message in this scanning interval, its status changes to the Up status again with the start of the next scanning interval.
Error Filter	Define which types of Syslog messages count for the Errors channel. To categorize received messages as error messages, define filters using a special syntax. The sensor collects messages until a scanning interval ends. As long as the scanning interval is running, the sensor does not change its status. By default, the sensor changes to the Down status after a scanning interval finishes and there was at least one error message during this scanning interval. The sensor shows the Down status at least until the succeeding scanning interval finishes. If the sensor does not receive any warning or error message in this scanning interval, its status changes to the Up status again with the start of the next scanning interval.

Sensor Display

Setting	Description
Primary Channel	Select a channel from the list to define it as the primary channel. In the device tree, PRTG displays the last value of the primary channel below the sensor's name. The available options depend on what channels are available for this sensor. You can set a different primary channel later by clicking below a channel gauge on the sensor's Overview tab.
Graph Type	Define how this sensor shows different channels: 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 generates a graph that visualizes the different components of your total traffic. You cannot use this option in combination with manual Vertical Axis Scaling (available in the channel settings).
Stack Unit	This setting is only visible if you select Stack channels on top of each other above. Select a unit from the list. PRTG stacks all channels with this unit 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.

Setting

Description

Primary Channel

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

You can set a different primary channel later by clicking below a channel gauge on the sensor's Overview tab.

Graph Type

Define how this sensor shows different channels:

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 generates a graph that visualizes the different components of your total traffic.
You cannot use this option in combination with manual Vertical Axis Scaling (available in the channel settings).

Stack Unit

This setting is only visible if you select Stack channels on top of each other above.

Select a unit from the list. PRTG stacks all channels with this unit 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 these settings are inherited from objects that are higher in the hierarchy. We recommend that you change them centrally in the root group settings if necessary. To change a setting for this object only, click under the corresponding setting name to disable the inheritance and to display its options.

For more information, see section Inheritance of Settings.

Debug Options

Setting	Description
Result Handling	Define what PRTG does with the sensor result: Discard result (default): Do not store the sensor result. Store result: Store the last sensor result in the \Logs\debug subfolder of the PRTG data directory on the probe system. The file name is UDP Debug Port [Port]_[Date].log. This setting is for debugging purposes. Use with caution. We recommend that you only use this setting for a short time because it can create huge data files.

Setting

Description

Result Handling

Define what PRTG does with the sensor result:

Discard result (default): Do not store the sensor result.
Store result: Store the last sensor result in the \Logs\debug subfolder of the PRTG data directory on the probe system. The file name is UDP Debug Port [Port]_[Date].log. This setting is for debugging purposes.
Use with caution. We recommend that you only use this setting for a short time because it can create huge data files.

Filter Rules

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 to monitor. 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[10.0.23.10/24]
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 matches. This value is not case-sensitive.)	message[Error]
data[id,param,value]	This checks the SD-ID block of the message's structured data for a parameter matching the specified value.	data[exampleSDID@12345,eventSource,Application]
data[parttext]	This checks if the specified substring matches structured data as displayed in the corresponding table.	data[exampleSDID@1234]
data[id,param]	This checks if the parameter exists in the specified ID element.	data[exampleSDID@1234,eventSource]

String parameters (except the substring in message) must 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 \Syslog Database subfolder of the PRTG data directory. 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.

Received 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 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.

You can automatically add a filter by clicking the content of a column.

Advanced Filter Settings

You can open advanced filter settings by clicking in the Filter row. The Advanced Filter appears in a popup window. In the text field, you can define a filter using the syntax as specified in section Filter Rules.

If you provided filter parameters on the Messages tab, the advanced filter already includes 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.

Channel List

Which channels the sensor actually shows might depend on the target device, the available components, and the sensor setup.

Channel	Description
Downtime	In the channel table on the Overview tab, this channel never shows any values. PRTG uses this channel in graphs and reports to show the amount of time in which the sensor was in the Down status
Drops	The number of dropped packets on the syslog port This channel has a default limit: Upper warning limit: 0.00000001
Errors	The number of messages categorized as "error" This channel has a default limit: Upper error limit: 0.00000001
Messages	The number of received Syslog messages This channel is the primary channel by default.
Warnings	The number of messages categorized as "warning" This channel has a default limit: Upper warning limit: 0.00000001