Which protocol is deployed through LAN automation to build node-to-node underlay adjacencies in SDA?

LAN Automation uses DNAC to zero-touch provision new network devices and configure IS-IS as the underlay routing protocol, automatically forming IS-IS adjacencies between seed and newly discovered fabric nodes. IS-IS provides the IP reachability in the underlay that the VXLAN data plane and LISP control plane of the SD-Access fabric rely on to function.

LISP is the overlay control plane protocol used by SD-Access for endpoint registration and location-identity separation, not the underlay routing protocol deployed by LAN Automation.

OSPF is not the underlay protocol used by Cisco LAN Automation in SD-Access; IS-IS is specifically chosen and configured by the automation workflow.

VXLAN is the data plane encapsulation technology for the SD-Access overlay and does not establish routing adjacencies or serve as an underlay IGP.