Menu
![](/uploads/1/2/5/3/125397246/396680885.jpg)
Skype for Business uses these ports and protocols:
How to make call. In Skype for Business Options window, you can make changes to the. Invite contacts to Skype audio calls, video calls or conferences.
5061 TCP (SIP) - Used for SIP/MTLS authentication of A/V users. Communications flow outbound through the internal firewall 443 TCP (HTTP) - Used by Skype for Business clients/Lync connecting from outside the intranet for SIP communications
1024-65535 UDP/TCP - Port range used for inbound and outbound media transfer through the external firewall
6891-6901 TCPPort range used by Skype for Business/Lync clients for file transfer
Make sure your firewall is not blocking these and it should work. I suspect that it is a firewall issue since it works internally on the same network.
-->
Note
If you're looking for information about dialing out from a Teams meeting, see Dialing out from a Teams meeting so other people can join it.
As the meeting organizer, you can dial out using the Skype for Business app to let other people join the same meeting using their phone. Although it's not required, when you are dialing out to someone, it's recommended that you dial the full number, including the country/region code. To get dial-out to work:
- You can dial-out only if you join a meeting using a Skype for Business app.
- You as the meeting organizer have been enabled for audio conferencing.
In order to add other participants via dial-out to the meetings of your organization, at least one authenticated user from the same organization as the organizer (your organization) is required to be present in the meeting in order to allow adding other participants via dial-out.
Note
We are frequently updating how you can manage features found in Skype for Business Online, so the steps here might be a little different.
Step 1: In the invite meeting, use the Invite More People option to dial out to a phone number.
Step 2: Enter the full phone number, including the country/region code in the box.
Supported countries and regions
Dial-out is only available to some countries/regions. For complete list, see Country and region availability for Audio Conferencing and Calling Plans.
Want to know more about audio conferencing?
Related topics
![](/uploads/1/2/5/3/125397246/396680885.jpg)