The MAC Address-based Forwarding Table Engine examines MAC address forwarding tables to determine Layer 2 connections. This link inference engine provides more accurate results when determining connections between Layer 2 devices and between Layer 2 and Layer 3 devices when MAC address forwarding tables are available for the devices.

In addition, the Link Layer Discovery Protocol (LLDP) Engine is helpful in determining Layer 2 and Layer 2/Layer 3 connections when LLDP is enabled on network devices. The Neighbor Discovery Protocol Engine is similarly helpful in determining Layer 2 and Layer 2/Layer 3 connections when a supported vendor-proprietary neighbor discovery protocol (such as Cisco Discovery Protocol) is enabled on network devices.