In a small number of environments where network connections are tightly controlled, you may need to make exceptions for classroom.cloud’s traffic within your network settings, firewall and/or antivirus solutions to ensure CC works as expected .
In the most cases, you can add a wildcard approved list of *.classroom.cloud  along with the Stun server domains and the IP addresses of the media servers.
Below is a list of servers with any protocols and ports that are used by classroom.cloud to communicate with the server:

Portal

• portal.classroom.cloud – HTTPS 443
• portal-westus.classroom.cloud – HTTPS 443

Authentication

• authentication.classroom.cloud – HTTPS 443
• authentication-westus.classroom.cloud – HTTPS 443

Gateways

• gw01pri01-westus.classroom.cloud – HTTPS 443
• gw01sec01-westus.classroom.cloud – HTTPS 443
• gw01mem01-westus.classroom.cloud – HTTPS 443

Tutor

• tutor.classroom.cloud – HTTPS 443
• tutor-westus.classroom.cloud – HTTPS 443

Student

• student-westus.classroom.cloud – HTTPS 443

Monitoring

• monitoring-westus.classroom.cloud – HTTPS 443

Signal

• signal-westus.classroom.cloud – HTTPS 443

Turn

• turn-westus.classroom.cloud – HTTPS 443
• turn1-westus.classroom.cloud – HTTPS 443
• turn2-westus.classroom.cloud – HTTPS 443

Media

• 13.83.95.105 – UDP 10000-22000
• 13.83.48.11 – UDP 10000-22000
• 104.210.59.59 – UDP 10000-22000
• 13.91.40.47 – UDP 10000-22000

API

• api.classroom.cloud – HTTPS 443
• api-westus.classroom.cloud – HTTPS 443
• apiinternal-westus.classroom.cloud – HTTPS 443
• safeguardingapi-westus.classroom.cloud – HTTPS 443
• teamsapi-westus.classroom.cloud – HTTPS 443

Functions

• functions-westus.classroom.cloud – HTTPS 443

Tenant Manager

• tenantmanager.classroom.cloud – HTTPS 443
• tenantmanager-westus.classroom.cloud – HTTPS 443