We all know that macros in Nagios 2 are very convenient, $HOSTADDRESS$, $HOSTNAME$ etc... with Nagios 3, it's even better! On-Demand macros are macros defined by the user. In Nagios 2, you can do the same thing with the $USERx$ macro but it is applied to all your hosts and services, whereas on-demand macros are applied to specific resources.

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