Which function does a Cisco SD-Access extended node perform?

While extended nodes connect non-fabric devices, their role is more about extending fabric services to traditional access layers rather than 'remote registration and configuration' as a primary function.

While the fabric uses tunneling, describing the extended node's role as performing 'tunneling between fabric and nonfabric devices to route traffic over unknown networks' is too vague and doesn't capture its specific function of integrating traditional L2 switches.

The primary function of a Cisco SD-Access extended node is to connect to downstream non-fabric-enabled (traditional) Layer 2 switches, effectively extending the SD-Access fabric to provide policy and segmentation for endpoints attached to those switches.

An extended node connects to downstream Layer 2 switches; its role is not to establish Layer 3 adjacencies with unmanaged nodes, but rather to manage policies for end devices via the fabric.