Nagios plug-in: check_dig

1) Copy the script to your Nagios 'libexec' directory
2) Change the CHECKNAME in the script to the hostname you want to resolve

Example: 
CHECKNAME="google.com"

Note: you may also need to change the location of bash in the script depending on your OS

3) Add the check_dig entry to your 'checkcommands.cfg'

Example:
# 'check_dig' command definition
define command{
        command_name    check_dig
        command_line    $USER1$/check_dig -h $HOSTADDRESS$
        }

4) Add an associated service into the 'services.cfg'

Example:
# Service definition
define service{
        use                             generic-service
        host_name                       INT_DNS
        service_description             DNS
        is_volatile                     0
        check_period                    24x7
        max_check_attempts              3
        normal_check_interval           5
        retry_check_interval            1
        contact_groups                  server-admins
        notification_interval           120
        notification_period             24x7
        notification_options            w,c,r
        check_command                   check_dig
        }

5) Restart Nagios