DNS
DNS (Domain Name Server) is a distributed database that links various host names to specific Internet addresses. The DNS monitor determines the IP addresses of external and internal host names by matching a virtual host name to an expected IP address. If a match is made, the status of the service monitor is OK.
You can, for example, use the DNS monitor to:
- ensure that your audience can access your Web site or portal by making sure that a selected address can be resolved
- identify instances in your network environment where resources have had their IP addresses changed, and now the resource is no longer available
To collect performance information, the DNS monitor:
- opens a UDP socket to a DNS server
- creates a query packet
- sends the query packet
- waits for a response
- parses the answers
The DNS monitor does not check for the NS or MX records, which return names and not IP addresses. Non-authoritative answers as well as authoritative responses are used.
Before You Begin
Before configuring the DNS monitor, determine the IP address for the host that you want to monitor. For internal hosts, you can use the ipconfig command from the command line.
The ipconfig command returns information similar to the following:
| No Format | ||
|---|---|---|
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Connection-specific DNS Suffix . . : idera.com IP Address . . . . . . . . . . . . : 10.1.1.42 Subnet Mask . . . . . . . . . . . .: 255.255.255.0 Default Gateway . . . . . . . . . .: 10.1.1.1 |
For external hosts, you can use the nslookup command from the command line as follows:
| No Format | ||
|---|---|---|
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nslookup <host name> |
The nslookup command returns information about the host, similar to the following:
| No Format | ||
|---|---|---|
| ||
Server: filter.idera.com Address: 10.1.1.100 Name: idera.com Addresses: 217.160.226.70, 10.1.1.95, 192.168.23.1, 192.168.190.1 |
Configuring DNS Monitors
To configure DNS monitors do the following:
- In the DNS monitor template, complete the monitor information fields.
To learn about monitor information fields, see Monitor Identification. - Complete the following fields:
- Hostname to Lookup
The host name that the monitor checks. The host name can be a Web site address, a server name, or a cluster name.
For example, for a Web site enter www.idera.com in this field. - Port
The number of the port on which the DNS server is listening. The default is 53. - IP Address
The IP address for which you want to check. If this address is not returned, the status of the service monitor becomes Critical. - Response Time
Enter the Warning and Critical Response Time thresholds for the amount of time required to complete a service check. For more information, see Configuring Warning and Critical Thresholds.
- Hostname to Lookup
- Click the Save for Graphing checkbox to save the data for a metric to the DataStore, which can be used to generate a report or graph.
- Complete the following settings:
- Timing Settings (see Adding Monitor Timing Settings Information for more information)
- Alert Settings (see Monitor Alert Settings for more information)
- Monitoring Period settings (see Monitor Timing Settings for more information)
- Alert Profile settings (see Alert Profiles for more information)
- Action Profile settings (see Action Profiles for more information)
- Click Finish.
...
TCP
The TCP monitor can determine whether a service or application is listening on a specific port. This monitor can also execute commands against an application or a service listening on a port and evaluate the result.
By extending the TCP monitor to evaluate the returned string based on a command over a network using TCP, you can test and monitor for a wide variety of responses.
For example, to have Uptime Infrastructure Monitor generate an alert if the file Weekly_Report was changed in your source code control system, you can send the string:
| No Format | ||
|---|---|---|
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get -e Weekly_Report1 |
and set the critical threshold value to 1.2 , where 1.1 represents no changes and 1.2 or greater represents one or more changes to the document.
Configuring TCP Monitors
To configure TCP monitors, do the following:
- In the TCP monitor template, complete the monitor information fields.
To learn how to configure monitor information fields, see Monitor Identification. - Complete the following fields:
Port
The number of the port on which the service or application that you want to monitor is listening.Info To check whether an application is listening on a port, leave the remaining TCP service monitor settings blank. - String to Send
The string that contains the command to which the service or application can respond. - Use SSL
Select this option if your connection uses SSL (Secure Sockets Layer) for security. - String to Receive
The string that is returned by the specified port and host. The string is the response to the command that was specified in the String to Send field. - Response Time
Enter the Warning and Critical Response Time thresholds. For more information, see Configuring Warning and Critical Thresholds.
- Click the Save for Graphing checkbox to save the data for a metric to the DataStore, which can be used to generate a report or graph.
- Complete the following settings:
- Timing Settings (see Adding Monitor Timing Settings Information for more information)
- Alert Settings (see Monitor Alert Settings for more information)
- Monitoring Period settings (see Monitor Timing Settings for more information)
- Alert Profile settings (see Alert Profiles for more information)
- Action Profile settings (see Action Profiles for more information)
- Click Finish.