# Automation Device Rules

This section will describe **Device Rules** in Cacti.

Cacti Automation relies on create device Rules these rules help the automation
process figure out what type of device is being scanned.  Based on the device
rule REGEX the automation engine can apply the appropriate template to the
device i.e if there is a REGEX for IOS.  The automation engine may pick the
Cisco router template for the device.

![Automation Device Rules](images/automation-device-templates.png)

Below you will be able to choose a REGEX that will help identify the device
the REGEX can be in any Perl supported format.  You can select either to
match by system description i.e the device hostname or the system name
i.e Cisco.

An example regex for Cisco would be (Cisco Internetwork Operating System
Software|IOS) This matches based on the system name of the Cisco IOS software.

Using this info automation would apply the appropriate device template you
choose.  If you see below we match for a system that matches Linux once a
device is found with that system name it is assigned the Net-SNMP device
template.

![Automation Device Rules Edit](images/automation-device-templates-edit1.png)

If the System/Device you are matching has a unique OID you can also match based
on that.

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