Legacy Manual

Variable Substitution

A number of the alert parameters allow you to insert a variable which will be substituted for a value when the alert happens.  Here is a list.

$dest The target destination's name (or IP Address if the IP didn't resolve to a name).  This is different than $host because an alert might be attached to an intermediate hop, whose information is accessed via the $host variable(s).  The final destination, though, is accessed via the $dest variable(s).
$destip The destination IP address
$destname The resolved DNS name for the destination
$config The name of the configuration used when tracing the target in question.  This is useful when you're using multiple configurations and want to be able to distinguish between them and the target name / IP isn't enough.  The $settings name is also equivalent to $config - either can be used interchangeably.
$host Host name (or IP address, if no name exists).  If used in an alert on a non-target hop, the alerting hop's information will be used.
$hostip The host IP address
$hostdnsname The resolved DNS name for the host
$year Current Year
$month Current Month
$day Current day of month
$hour Current hour
$minute Current minute
$second Current second
$date Same as $year-$month-$day.
$time The same as $hour$minute - note the absence of any punctuation - that's to make sure the file name is valid, if this mask is being used in a file name.