Add / Edit a DNS Task

 

Device Type: ServerView Platform

Glossary: DNS Task

How to create devices and tasks

How to Edit a DNS Task

Once you have created a device and are adding or editing a DNS task, you will be prompted to adjust the following settings:

DNS_pump_sept.12.13

The DNS monitoring task has the following configurable options:

Task Name

Provide a descriptive name for the task so that you would be able to identify the task later among a list of similar tasks.  For example, “www.example.com DNS”

Maximum Connection Timeout (in seconds)

Enter the number of seconds the task should wait for a response from the web page before returning an error.  The task will continue to run past the Max timeout in order to record the actual time it takes.  If this is left blank the default timeout for a task is 120 seconds.

DNS Server

Enter the url name, IPv4 or IPv6 address of the DNS server you wish to poll.  If you do not enter a value the field will automatically be filled with ‘a.root-servers.net’ and a random root server (from A to M) will be polled each time.

Host Name to Resolve

Enter the url that you wish to resolve.  The address should be formed exactly as you would use it in a browser such as www.example.com.  You should not include a proceeding https://.

Record Type

Select which NS record type to query.  The record type only defines the content of the query, it does not automatically define what the expected response will look like.  You must still explicitly define the expected response in the Expected Answer field based upon your query.  In addition, the Expected Authority and Expected Additional fields can also be used to validate the query response.

A

IPv4 address record that maps a hostname to an IPv4 address.

AAAA

IPv6 address record that maps a hostname to an IPv6 address.

NS

Name server record that delegates the authoritative name servers.

CNAME

Canonical name record that is an alias to another name record.

SOA

Start of authority record returns the most authoritative information regarding the domain, mail and record timing information.

TXT

Text Record can be used for general information as well as Sender Policy Information or other machine readable information.

MX

Mail exchange record defines the message transfer agents for the domain.

PTR

Pointer record points to a canonical record for reverse dns lookup.

SPF

Sender Policy Framework is a legacy record that is now generally handled in the TXT record.

Info

“PTR” Record Type causes a reverse DNS look-up. Host name to Resolve in this case should contain a reversed IP address in the following format:

For IPv4:

If the IP address is 10.12.34.56

The expected response would be 56.34.12.10.in-addr.arpa

For IPv6:

A reverse DNS look-up uses the special domain “ip6.arpa.”:

5.4.3.2.1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.

where “5.4.3.2.1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2” is a reversed IP address. 2001:0db8::1:2345 is the non-reversed original.

NOTE
*Selecting the record type only affects the DNS query content. The record type content validation is only based on references given in an ‘Expected Answer’ section. The ‘Expected Authority’ and ‘Expected Additional’ fields can also be used for record type validation depending on the exact configuration.

Recursion Desired Flag

Enables or disables the recursion desired (RD) flag in outgoing DNS queries.  Most applications such as internet browsers enable the RD flag by default so that they receive a successful DNS resolution even if the DNS server queried does not have a valid response.  In this case the DNS server queried will contact a top level DNS server and follow the result path until it has received an authoritative result.

NO

The DNS query will not send an RD flag if you only wish to perform a single iteration to see if the selected DNS server resolves the target in one hop or not.

YES

Requests that the DNS server perform recursion for the monitoring service (ie. the remote server will scan a DNS tree for the monitoring service in search of an appropriate result).

*Client applications (such as Internet browsers) typically use the RD flag.

Verify Response

Defines how a DNS  answers with a required record type are interpreted.

All Servers

Answers only from end-leaves of DNS tree are verified for proper response.  NOTE that you will encounter more random failures from root servers timing out if you require a successful response from all root servers.  This does not necessarily indicate an outage, rather it may indicate that one or more root servers are under a heavy load and did not respond in time.

First Server

Only the first found answer with a desired record type is further analyzed. The first appropriate answer is also considered the end of a DNS tree.

Ignore Timeouts From  (Servers Timeout Filter)

When querying multiple servers it is common to receive a timeout from one or more servers.  This filter allows you to specify whether you want to ignore such timeouts or if you wish to receive alerts for these timeouts.  Options include alert on all timeouts, filtering out network and time-out errors from exact hosts, or a range of nodes based on a mask.

* symbol

All network-related and timeout errors are included and will trigger alerting.

Empty field

The engine ignores all network-related and timeout errors. .

If a mask is added

The engine ignores all network-related and timeout errors of the matching host or IP address.

Individual examples

IPv4: 192.168.* filters any address beginning with 192.168.

IPv6: 2001:501:* filters any address beginning with 2001:501:

url: len*a.ru filters any url that begins with len and ends with a.ru

Multiple servers are divided by a semi-colon

2001:501:* ; len*ra.ru

Expected Answer

If the returned string result includes the value entered in the expected answer field the task returns a success.  You can use logical expressions to define more complex results.

For example  can you use:  10.0.0.1 | 127.0.0.1 | 192.168.1.1

If any of the specified IP addresses occur in the returned string then the query will be considered a success.

Expected Authority

Parses the response to retrieve the value in the Authority section.

Expected Additional

Shows additional resource records returned.  If there are multiple DNS servers in the list this may return quite a few results.

An example of complex constructions

(answer[1].Name=tut.by | answer[2].Name=google.com) & !answer[1].Type=A & 'additional[2].Name=ns2.company.com' & key value | fftb

The final two adjustments are only suitable when a custom DNS server is specified in the ‘DNS Server’ field (not a ROOT server and not specified by a direct IP address).

DNS Resolve Mode

Determines which mode to utilize to resolve an NS address.  Read the DNS Resolve Mode article For more Details.