Teams Mobile App - Audio connection lost after change between mobile network and wifi

Brass Contributor

Hello all, 


we have a problem with the mobile Teams app when changing between mobile data and wifi

We're using an Unify OpenScape Voice with an OpenScape SBC for the connection between MS and our local PBX.

We are using Media Bypass.



Scenario: MS Teams Call: -- Good case

When we have an established Teams to Teams call and the mobile app is changing the network Teams will connect the audio connection after some seconds. 



Scenario: MS Teams Direct routing Call: -- bad case

When their is an established MS Teams Direct Routing call and the mobile app is changing the network the audio connection will not be connected. We have to end the call and start a new call. Doesn't matter if the change is from Wifi-Mobile / Mobile-Wifi. 


Looks like the IP Adresses are not updated during the SIP Call. 

Is there the same behaviour with another SBC? 


Following findings from our vendor: 

The call is established correctly but when there is a change from WLAN to LTE, the SBC stops receiving SRTP packets from MS Teams.
The same applies for the firewall. No SRTP packets are received from MS Teams and consequently not sent to the SBC.
On the other hand, the SBC (and the firewall) keeps sending outgoing SRTP packets during the whole time and never stops until the call is ended.

The signaling negotiation is performed with Microsoft Phone system from IP
Inside the SDP, we can see that Microsoft Phone system requests the SRTP packets to be sent to Microsoft Media Processor with IP

It does not seem to be any issue with the SBC or the firewall.
It would be advisable to open a ticket to Microsoft and inform us why they stop sending SRTP packets after the change from WLAN to LTE.


Microsoft Teams replies with an ACK and the SRTP messages start being exchanged.
Immediately after, MS Teams sends a re-Invite, containing the same info and so does the SBC. As a result, no change is made in the IPs and ports used for the SRTP exchange.
After this time and until the end of the call, the is no re-Invite requesting a change in the IP or port used.


the change from WLAN to LTE is performed. After this time, no SRTPs are received from either the firewall or the SBC:


On the other hand, the SBC keeps sending SRTPs to the already agreed ip and port, as it is not informed of any change.
It continues to do so until, when the call is ended.





Thank you very much 



Best regards, 


2 Replies

Hi @DominikA9522 ,


If you are experiencing audio connection issues in the Microsoft Teams mobile app when switching between mobile networks and Wi-Fi, there are a few troubleshooting steps you can try to resolve the problem:

1. Check your network connection: Make sure you have a stable and reliable network connection, either through Wi-Fi or mobile data. Poor network connectivity can cause audio disruptions. Try switching between Wi-Fi and mobile data to see if the issue persists on both connections.

2. Restart the Teams app: Close the Teams app completely and reopen it. This simple step can help resolve minor glitches and refresh the app's connection.

3. Clear app cache (Android): If you are using an Android device, clearing the app cache can sometimes resolve issues. Go to your device's Settings, find the Apps or Applications section, locate Microsoft Teams, and choose the option to clear the cache. Please note that this may log you out of the app, so make sure you know your login credentials.

4. Reinstall the Teams app: If the problem persists, try uninstalling and reinstalling the Microsoft Teams app on your mobile device. This can help fix any potential software issues or corrupted files.

5. Update the app: Ensure that you have the latest version of the Teams app installed on your device. Developers often release updates to address bugs and improve app performance.


Remember, these troubleshooting steps are general recommendations, and the exact steps or options available may vary depending on your specific device and operating system version.



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@Deleted Thanks for your answer. The error just appears by a direct routing call. The Audio conenctions is lost completely and a new calls has to be made. 

In an Teams Call the audio comes back after some seconds...