In a Cisco SD-Access solution, an extended node connects to a single edge node using the 802.1Q protocol. This protocol allows for the transmission of traffic from multiple VLANs over a single link, which is essential for the extended node to communicate with the fabric edge node.The 802.1Q trunking protocol encapsulates Ethernet frames with a VLAN tag, enabling the frames to be properly routed through the fabric and maintaining the segregation of traffic between different VLANs. Reference: https://www.cisco.com/c/en/us/td/docs/solutions/CVD/Campus/cisco-sda-design-guide.html#Network