PRTG Manual: DNS Sensor
The DNS sensor monitors a Domain Name System (DNS) server. It resolves a domain name and compares it to a specific IP address. The sensor checks the answer section as well as the additional section, if one was sent.
The sensor can show the following:
- Response time of the DNS server
- The Down status if the DNS server does not correctly resolve a specified domain name
- Dutch: DNS
- French: DNS
- German: DNS
- Japanese: DNS
- Portuguese: DNS
- Russian: DNS
- Simplified Chinese: DNS
- Spanish: DNS
- This sensor supports the IPv6 protocol.
- This sensor has a very low performance impact.
- If the address of the parent device is a fully qualified domain name (FQDN) or NetBIOS name, PRTG also includes the time it takes to resolve this address in the response time measurement.
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 do not see all setting fields in this dialog. You can change (nearly) all settings in the sensor's Settings tab later.
Click the Settings tab of a sensor to change its settings.
Usually, 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.
Setting |
Description |
---|---|
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 the sensor inherits from its parent device, parent group, and parent probe. This setting is shown for your information only and cannot be changed here. |
Tags |
Enter one or more tags. Confirm each tag with the Spacebar key, a comma, or the Enter key. You can use tags to group objects and use tag-filtered views later on. Tags are not case-sensitive. Tags are automatically inherited.
The sensor has the following default tags that are automatically predefined in the sensor's settings when you add the sensor:
|
Priority |
Select a priority for the sensor. This setting determines the position of the sensor in lists. The highest priority is at the top of a list. Choose from the lowest priority ( |
Setting |
Description |
---|---|
Timeout (Sec.) |
Enter a timeout in seconds for the request. If the reply takes longer than this value, the sensor cancels the request and shows a corresponding error message. Enter an integer value. The maximum value is 900 seconds (15 minutes). |
Port |
Enter the number of the port to which the sensor tries to connect. This must be the port that the sensor's parent device runs the DNS service on. Usually, you use port 53. We recommend that you use the default value.
|
Domain |
Enter the domain name that the sensor resolves using the DNS server specified in the sensor's parent device settings. You can enter an internet domain name here (for example, example.com) or a DNS name in your internal network (such as computer-xyz), depending on the type of DNS server you monitor. You can also enter an IP address, but an error might occur with certain query types. |
Query Type |
Select the query type that the sensor sends to the DNS server:
|
Check Result |
Define if the sensor checks the result from the DNS server:
|
Value |
This setting is only visible if you enable Check result above. Enter elements that the response of the DNS server must contain. Enter each entry in one line. The received result must contain at least one of the elements. If none of the elements matches the response, the sensor shows the Down status. For example, you can enter an IP address here if your Domain field contains a host name. Only if the host name is resolved to the correct IP address, your sensor shows the Up status. |
Result Handling |
Define what PRTG does with the sensor result:
|
Setting |
Description |
---|---|
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.
|
Graph Type |
Define how different channels are shown for this sensor:
|
Stack Unit |
This setting is only visible if you enable Stack channels on top of each other as Graph Type. Select a unit from the list. All channels with this unit are 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. |
By default, all of the following settings are inherited from objects that are higher in the hierarchy. You should 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. You then see the options described below.
For more information, see section Inheritance of Settings.
Click to interrupt the inheritance.
Setting |
Description |
---|---|
Scanning Interval |
Select a scanning interval from the dropdown list. The scanning interval determines the amount of time that the sensor waits between two scans. Choose from:
|
If a Sensor Query Fails |
Select the number of scanning intervals that the sensor has time to reach and to check a device again if a sensor query fails. Depending on the option that you select, the sensor can try to reach and to check a device again several times before the sensor shows the Down status. This can avoid false alarms if the monitored device only has temporary issues. For previous scanning intervals with failed requests, the sensor shows the Warning status. Choose from:
|
Schedules, Dependencies, and Maintenance Window
You cannot interrupt the inheritance for schedules, dependencies, and maintenance windows. The corresponding settings from the parent objects are always active. However, you can define additional schedules, dependencies, and maintenance windows. They are active at the same time as the parent objects' settings.
Setting |
Description |
---|---|
Schedule |
Select a schedule from the list. You can use schedules to monitor during a certain time span (days or hours) every week. Choose from:
|
Maintenance Window |
Select if you want to set up a one-time maintenance window. During a maintenance window, monitoring stops for the selected object and all child objects. They show the Paused status instead. Choose between:
|
Maintenance Begins |
This setting 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 one-time maintenance window. |
Maintenance Ends |
This setting is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the end date and time of the one-time maintenance window. |
Dependency Type |
Select a dependency type. You can use dependencies to pause monitoring for an object depending on the status of a different object. You can choose from:
|
Dependency |
This setting is only visible if you enable Select a sensor above. Click |
Dependency Delay (Sec.) |
This setting is only visible if you enable Select a sensor above. Define a time span in seconds for the dependency delay. After the master sensor for this dependency returns to the Up status, PRTG additionally delays the monitoring of the dependent objects by the time span you define. This can prevent false alarms, for example, after a server restart or to give systems more time for all services to start. Enter an integer value.
|
Click to interrupt the inheritance.
Setting |
Description |
---|---|
User Group Access |
Define the user groups that have access to the sensor. You see a table with user groups and group access rights. The table contains all user groups in your setup. For each user group, you can choose from the following group access rights:
|
For more information about sensor settings, see the following sections: