APIC not discovering hosts in campus environment

After performing a discovery on  network,  noticed that a significant quantity of  hosts were missing from the host inventory. Desided to do a discover on a small portion of my network and received the following:

As you can see the discovery is finding many hosts, however they are NOT showing up in the host inventory.  Currently ip device tracking is turned off due to an issue experienced windows .

That would be the issue.  You need IP device tracking for wired hosts.

 There are also some traps that are used from switches to get quick updates when link status changes.

 See documentation for details:

Cisco Application Policy Infrastructure Controller Enterprise Module Configuration Guide, Release 1.3.x - Device Config…

SNMP Trap Configuration

 To ensure that Cisco APIC-EM captures data about the hosts connected to your network devices, you must set up SNMP traps or notifications. Enter the following SNMP commands to set up SNMP traps on the devices that connect to hosts within your network:

1. snmp-server enable traps snmp linkdown linkup
2. snmp-server host IP address version 2c public

Note	For Cisco Nexus devices, enter the following SNMP commands instead of the commands listed above: snmp-server enable traps snmp linkdown linkup snmp-server host IP address use-vrf default

After configuring SNMP traps on the network devices, the following data is captured and made available in the controller's GUI:

• Host data including the MAC address, IP address, and type
• Device interface status

How to enable IP tracking .

• You can do it from the controller,
• admin->settings -> device controllability -> IPDT Autoconfig
•  or from the CLI
• IP Device Tracking (IPDT) Overview - Cisco