Understanding Computer system port history

When we get inventory for a computer, it includes the network interfaces for the computer, and we also get the MAC address for those interfaces. You can see this just in the section above the Port History on the Network page of the properties of a Windows computer. Let's park this for the moment. 

Under Administration > Networks you can configure network scanning and optionally include SNMP discovery, with SNMP credentials to suit your printers, switches, routers, etc. This will get inventory for switches and routers and may include a list of ports, and the MAC addresses attached to the ports. You can see this if you open the properties of a device in Network Devices > Switches and Routers, and then if you look at the Attached Devices page of that you can see that SNMP inventory gets the MAC address of attached devices. 

So, if a MAC from SNMP inventory matches a MAC from computer system network interface inventory, then because MAC addresses are typically universally unique, Certero can link the computers to switch ports, and you can jump between them via that link by clicking on switch names in computer Port History (even though they are not underlined) and by clicking on device names in the switch/router Attached Devices properties page. 

Each time we get inventory for a computer or a switch, the current relationship between the computer and switch port is re-evaluated and the previous relationship (if it's different) is added to the computer's port history. 

If port history is missing for a computer, then the most likely cause is that there is no network discovery correctly configured to find and inventory the switch that the computer is attached to.