The Discovery tasks feature was first introduced in IP Fabric version 3.5.2 as a fast discovery enablement for large scale networks. When enabled, it will use current ‘Discovery History’ database (in Management > Discovery History) only when creating a new snapshot without detecting any new network devices during the discovery process.
If limit is disabled and discovery crawl through whole network is performed, you can choose which options will be used for new devices detection (ARP, CDP/LLDP, Routing Table records or a Traceroute). Default is to use all available options.
The feature is especially helpful for large complex networks with already defined device scope to avoid multiple repetitive failed SSH/Telnet attempts that may slow down snapshot creation.