====== Background ======
Following is a general definition of the technology that lays behind DNSMonitor.

  * DNSMonitor users the nslookup command
    * nslookup sends queries to Internet domain name servers. It is used to display the name and requested information for a host or domain.

====== Options ======
{{technology:zenoss:about:dnsmonitor.png?497×429}}

There are a handful of important fields:
  * hostname
    * The domain name or url you want to query
  * dnsServer
    * DNS server you want to use for the lookup
  * expectedIPAddress
    * the IP you expect the hostname to resolve to
  * severity
    * the severity of an event, if thrown
  * cycle time
    * how often the domain is checked

====== check_dns Documentation ======
Following is the documentation from the nagios version of the same implementation, which Zennos's is based off of. Very similar functionality and provides some more detailed descriptions.

<code>
$ $ZENHOME/libexec/check_dns --help
check_dns (nagios-plugins 1.4.5) 1.54

This plugin uses the nslookup program to obtain the IP address for the given host/domain query.
An optional DNS server to use may be specified.
If no DNS server is specified, the default server(s) specified in /etc/resolv.conf will be used.

Usage:check_dns -H host [-s server] [-a expected-address] [-A] [-t timeout] [-w warn] [-c crit]

Options:
 -h, --help
    Print detailed help screen
 -V, --version
    Print version information
 -H, --hostname=HOST
    The name or address you want to query
 -s, --server=HOST
    Optional DNS server you want to use for the lookup
 -a, --expected-address=IP-ADDRESS|HOST
    Optional IP-ADDRESS you expect the DNS server to return. HOST must end with .
 -A, --expect-authority
    Optionally expect the DNS server to be authoritative for the lookup
 -w, --warning=seconds
    Return warning if elapsed time exceeds value. Default off
 -c, --critical=seconds
    Return critical if elapsed time exceeds value. Default off
 -t, --timeout=INTEGER
    Seconds before connection times out (default: 10)
</code>