According to this Cisco link (Table 5), the following ports are from Cisco DNA Center to fabric underlay switches:
+ TCP 22: From Cisco DNA Center to fabric switches' loopbacks for SSH
+ TCP 23: From Cisco DNA Center to fabric switches' loopbacks for TELNET
+ UDP 161: From Cisco DNA Center to fabric switches' loopbacks for SNMP device discovery
+ ICMP: From Cisco DNA Center to fabric switches' loopbacks for SNMP device discovery
+ TCP 443: From Cisco DNA Center to fabric switches for software upgrades (also to the internet if there is no proxy)
+ UDP 6007: From Cisco DNA Center to switches and routers for NetFlow
+ UDP 123: From Cisco DNA Center to fabric switches for the initial period during LAN automation So in fact there are three correct answers for this question, including TCP 23, ICMP and UDP
6007 but there are two best answers TCP 23 and ICMP (which match "fabric switches" in the question).
https://www.cisco.com/c/en/us/td/docs/cloud-systems-management/network-automation-and- management/dna-center/2-1-
2/install_guide/2ndGen/b_cisco_dna_center_install_guide_2_1_2_2ndGen/m_plan_deployment_
2_1_2_2ndgen.html

Control-Plane Nodes Map System that manages Endpoint to Device relationships Fabric Border Nodes A Fabric device (e.g. Core) that connects External L3 network(s) to the SDA Fabric Fabric Edge Nodes A Fabric device (e.g. Access or Distribution) that connects Wired Endpoints to the SDA Fabric Fabric Wireless Controller A Fabric device (WLC) that connects APs and Wireless Endpoints to the SDA Fabric Reference: https://www.cisco.com/c/dam/m/hr_hr/training-events/2019/cisco-connect/pdf/VH- Cisco-SD-Access-Connecting.pdf