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Inquiry regarding Teams Media Codecs, Protocols, and Unlisted IP Ranges (48.x and 20.x) detected during Packet Analysis

kdh 0 Reputation points
2026-02-03T13:14:58.9166667+00:00

Hi Microsoft Teams Community,

I am currently performing a detailed packet analysis to monitor and troubleshoot the call quality of Microsoft Teams within our client environment. To ensure an accurate analysis, I would like to request official confirmation on the following technical details.

  1. Media Codecs for Audio and Video: I would like to identify the exact codecs used in the current version of Teams.
  2. Communication Protocols: I am observing various traffic patterns and want to verify the protocols used for media transport. Does Teams still primarily use SRTP over UDP (ports 3478-3481)? In what specific scenarios does it fallback to STUN/TURN or TCP/443?
  3. Clarification on Unlisted IP Ranges (48.x and 20.x) According to the official documentation (Office 365 URLs and IP address ranges - ID 11), the primary ranges are listed as 52.112.0.0/14, 52.122.0.0/15, and 2603:1063::/38. However, during my packet capture, I have detected significant traffic from the following ranges:
  • 48.x.x.x (e.g., 48.x.x.x)
    • 20.x.x.x (e.g., 20.x.x.x)
    These appear to be Microsoft Azure public IP blocks, but they are not explicitly listed in the "Teams" specific section of the official documentation. Could you confirm if these ranges are now officially used for Teams Media Optimization or Transport Relays? If so, why are they missing from the ID 11 Teams-specific list, and should we officially whitelist the entire Azure IP range for Teams quality?

I look forward to your technical guidance to help us refine our network configuration.

Best Regards,

KDH

Moved from Microsoft Teams | Development

Microsoft Teams | Microsoft Teams for business | Other
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  1. Doris V 540 Reputation points Microsoft External Staff Moderator
    2026-02-04T03:51:08.4933333+00:00

    Hello @kdh, 

    Thank you for posting your question in the Microsoft Q&A forum. 

    Below is the officially documented behavior we can confirm publicly, plus guidance on what to do with the 20.x / 48.x addresses you’re seeing: 

    1. Media codecs 
    1. Protocols, ports, and “fallback” behavior 
    1. For your question about whitelist “all Azure” 

    Microsoft does not recommend whitelisting the entire Azure public IP space for Teams. Instead, Microsoft’s model is: 

    • Allow the published Microsoft 365 endpoints (and keep them updated).  
    • Use the endpoint web service (rather than manual static lists) because it is updated on an ongoing cadence. 

    If you need more advanced or highly technical guidance, I recommend posting your question on Stack Overflow. The community there includes many experienced developers who can provide deeper insights and coding‑specific support. 

    Note: Please understand that as a forum moderator, my primary goal is to provide helpful guidance and support through general troubleshooting steps. While I don’t have access to internal systems or test devices required to resolve backend/account issues, I truly appreciate your understanding of these limitations.  

    Thank you for choosing Microsoft, and I am looking forward to your response. If anything is unclear, please don’t hesitate to reach out to me. 

     If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have any extra questions about this answer, please click "Comment."    

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