To begin discovering devices on your network immediately, configure a collector to execute passive monitoring first. Passive discovery provides instantaneous network updates and broadens understanding of a network's core.
The passive discovery types are Broadcast, OSPF, and BGP. 
Passive discovery is not impacted by a collector's rescan interval because passive discovery never sends out packets. 
The rescan interval only comes into play for active discovery methods configured on a collector such as Host Discovery and Path Discovery.
Configure Broadcast Monitoring
Broadcast Discovery gathers IP address information from the forwarding devices on your network by "listening" to ARP, DHCP, and ICMPv6 for IP and MAC addresses. Select the protocols you wish to use, then click Update.
- Select the Broadcast tab and click Edit.
The Broadcast Configuration form displays.
- Select the protocols you wish to enable and click Update.
Broadcast Discovery is enabled.
Configure BGP
To see which protocols are the most responsive in your network, browse to Reports > Browse Real-Time and check out the Discovery Statistics by Protocol report.
