Most Cloud SWG connectivity and authentication methods require communication through specific ports, protocols, and services
Symantec Enterprise Agent
WSS Agent
SEP Agent (Tunnel Mode)
The following Cloud SWG domains need to be resolved to their correct IP address.
threatpulse.net
saml.threatpulse.net
ctc.threatpulse.com
pod.threatpulse.com
client-id.wss.symantec.com
Configuration issues could arise if these domains get DNS poisoned or do not resolve correctly to their IPs.
Reference: