Fabric Connect, Auto-Sense, and Auto-Configuration
Fabric Connect automation appears in three related but distinct mechanisms, and exam questions usually test whether you can say which one does what.
Fabric Attach (FA)
FA is an LLDP-based signalling protocol. An FA client (an EXOS switch, an access point, a camera) sends TLVs requesting service; an FA server or proxy on the VSP assigns the I-SID and VLAN, so the access device never needs fabric CLI. FA elements are identified by an element ID, and assignments appear in show fabric attach output. It requires LLDP enabled and a continuous path of FA-capable devices.
Auto-Sense
Auto-Sense provisions a UNI port from a template after identifying the attached device - using MAC OUI, DHCP fingerprinting (vendor class) or LLDP. On a match, the switch applies the associated Auto-Sense configuration: VLAN membership, Fabric Attach I-SID, QoS. It removes the manual 'configure 200 phone ports' step, but the template and detection rules must exist first.
Zero Touch Fabric (ZTF)
ZTF brings up a factory-default VSP without console work: the switch obtains an address by DHCP, the DHCP server returns vendor option 43 sub-options carrying fabric parameters (nickname, fabric/B-VID, management details), and the node configures IS-IS/SPBM on its uplinks and joins the fabric.
Worked example
An IP phone is plugged into port 1/3 of a VSP 7400. Auto-Sense matches the phone's OUI to the 'voice' template, which places the port in VLAN 200 and tags it with Fabric Attach I-SID 200200. The FA server carries that I-SID across the fabric to the remote BEB where the call server sits, and nothing was typed on the port. Reasoning: Auto-Sense answered 'what is this device and which template applies'; FA answered 'which service does it get and where does it go'; ZTF would have answered 'how did this switch join the fabric at all'.
Traps
Treating the three as synonyms - Auto-Sense is port provisioning, FA is service signalling, ZTF is node onboarding. Expecting FA to work through a non-LLDP hub or unmanaged switch. Forgetting that Auto-Sense needs a defined template. Enabling ZTF without a DHCP option 43 plan, so the switch boots unconfigured. Assuming the FA client picks the VLAN, when the server actually dictates the I-SID and VLAN assignment.