| Service and Protocol | Port | CCE | Teams
Direct
Routing | Description | Connectivity Check Results |
|---|
| Inbound |
| SIP/MTLS (TCP) | 5061 |  Image Removed Image Added | | Handles signaling for voice communications | |
| STUN (TCP) | 443 | Image RemovedImage Added | | STUN/TURN negotiation of candidates | |
| STUN (UDP) | 3478 | Image RemovedImage Added | | Determines the version of the Edge Server with which the
Skype server is communicating | |
| SIP/TLS (TCP) | 5061 | | Image RemovedImage Added | Handles signaling for voice communications; primary and secondary server IP addresses are hard-coded. | |
| RTP (UDP) | 16384 - 17584 | | Image RemovedImage Added | Handles media for voice communications | |
| Outbound |
| DNS (UDP/TCP) | 53 | Image RemovedImage AddedImage Removed | Image Added | For the service that resolves the Public FQDN for the Microsoft Signaling Server, the Connectivity Check populates a default destination from the Host Name and Domain Name attributes in Host Information (that is, Web UI's Settings > System > Node-Level Settings). The tool opens the UDP socket and sends a homemade DNS packet. | If the remote server responds with a DNS response packet the port is reported as open. Otherwise, the port is reported as closed. |
| NTP (UDP) | 123 | | Image RemovedImage Added | Service to support timestamps in certificate usage | |
| HTTP (TCP) | 80 | Image RemovedImage Added | | Certificate revocation check and Certificate Revocation
List (CRL) retrieval The host field is filled by default with the FQDN found in the SBC certificate, under the attribute: CRL Distribution Point. | |
| RTP (UDP) | 49152-65535 | | Image RemovedImage Added | Handles media for voice communications | |
| SIP/TLS (TCP) | 5061 | | Image RemovedImage Added | Handles signaling for voice communications; primary and secondary server IP addresses are hard-coded. For Teams Direct Routing, the SIP target can be the Microsoft SIP signaling server; Connectivity Check routes to: sip.pstnhub.microsoft.com, sip2.pstnhub.microsoft.com, sip3.pstnhub.microsoft.com. | |
| STUN (TCP) | 443 | Image RemovedImage Added | | For the service handling STUN/TURN negotiation of candidates, the Connectivity Check opens a UDP socket and sends a homemade STUN packet. | If the remote server does not respond with a STUN error packet, the port is reported as closed. The remote peer is the Microsoft Cloud Edge Server and the STUN protocol determines the Public IP address. |
| STUN (UDP) | 3748 | Image RemovedImage Added | | For the STUN service that determines the version of the Edge Server with which the Skype server is communicating, Connectivity Check populates a default destination from from the Host Name and Domain Name attributes in Host Information (that is, Web UI's Settings > System > Node-Level Settings). The tool opens the UDP socket and sends a homemade DNS packet. | If the remote server responds with a DNS response packet the port is reported as open. Otherwise the port is reported as closed. |
| SIP/MTLS (TCP) | 5061 | Image RemovedImage Added | | Service to resolve Microsoft Signaling Server Public FQDN For CCE, the Connectivity Check routes to sip.YourSbcDomain | |