When you join a Teams video call from a corporate VPN, the call often drops after a few minutes or freezes and reconnects repeatedly. This usually happens because the VPN tunnel adds latency or blocks the UDP media ports that Teams needs for real-time audio and video. In this article, I will explain why the VPN breaks Teams media, show you how to configure the VPN client and Teams policies to prevent drops, and list additional checks if the problem persists.
Corporate VPNs encrypt all traffic and route it through a gateway, which can introduce jitter and packet loss. Teams uses UDP on ports 3478 through 3481 for media; if the VPN blocks or throttles these ports, the call falls back to TCP, which is slower and more prone to disconnects. You will learn how to allow UDP traffic, enable split tunneling, and adjust Teams network settings to keep video calls stable.
Key Takeaways: Stabilize Teams Video Calls Over a Corporate VPN
- VPN client split tunneling: Exclude Teams media IP ranges from the VPN tunnel to reduce latency and packet loss.
- Teams admin center > Meetings > Meeting policies > Media bit rate: Lower the maximum bit rate to reduce bandwidth demands that cause drops.
- Teams client > Settings > Devices > Disable hardware acceleration: Turn off GPU processing if video stutters or freezes during calls.
Why a Corporate VPN Causes Teams Video Call Drops
Teams media traffic uses UDP on ports 3478 to 3481. These ports carry real-time audio and video. A corporate VPN typically encrypts all traffic and sends it through a central gateway. This adds two problems: latency and packet loss. When UDP is blocked or throttled, Teams automatically falls back to TCP, which is slower and less reliable for real-time media. The result is a call that drops or freezes.
Another factor is VPN split tunneling. Many VPNs are configured to route all traffic through the tunnel. If your VPN does not allow split tunneling, Teams cannot send media directly to Microsoft servers. Instead, all packets travel through the VPN gateway, which may be far from the meeting server. This increases round-trip time and causes timeouts.
Finally, corporate firewalls often inspect UDP traffic. Deep packet inspection can add delay or drop packets that look unusual. Teams uses SRTP, which is encrypted, so inspection may cause the firewall to drop the packets. The fix is to allow UDP traffic on the required ports and to bypass inspection for Teams media.
How Teams Chooses Media Paths
Teams uses a media path that is separate from the signaling path. Signaling uses HTTPS on port 443. Media uses UDP on ports 3478 to 3481. If the VPN blocks UDP, Teams tries TCP on port 443, but this is not optimal for video. A stable video call requires a direct UDP path with low latency and minimal packet loss.
Steps to Configure the VPN and Teams to Prevent Call Drops
Follow these steps in order. Start with the VPN client, then adjust Teams settings. If you are not the IT administrator, ask your IT team for the VPN and policy changes.
- Enable split tunneling in your VPN client
Open your VPN client, usually Cisco AnyConnect, GlobalProtect, or FortiClient. Find the split tunneling settings. Add the Microsoft Teams media IP ranges to the split tunnel exclusion list. This allows Teams media to go directly to Microsoft servers without passing through the VPN. The IP ranges are listed in Microsoft 365 URLs and IP address ranges. If you cannot edit the VPN client, ask your IT team to update the VPN configuration. - Allow UDP ports 3478 to 3481 on the firewall
If split tunneling is not possible, ensure the corporate firewall allows outbound UDP on ports 3478 to 3481. Also allow UDP on ports 50000 to 50019 for Teams media in some regions. Check your firewall logs for blocked UDP packets to these ports. Contact your network administrator to add the rules. - Disable hardware acceleration in Teams
In Teams, click your profile picture, then select Settings. Go to Devices and toggle off Hardware acceleration for video calls. This reduces GPU load and can prevent video freezes that lead to drops. - Lower the media bit rate in Teams policy
If you are an admin, go to the Teams admin center. Under Meetings, select Meeting policies. Edit the global policy or create a new one. Set Media bit rate to a lower value, such as 1.5 Mbps. This reduces bandwidth usage and lessens the chance of packet loss on a VPN. - Update the VPN client and Teams to the latest versions
Outdated VPN clients have bugs that cause UDP drops. Update your VPN client from the vendor website. Also update Teams by clicking your profile picture and selecting Check for updates. Restart both applications after updating.
If Teams Still Has Issues After the Main Fix
Teams Call Drops Only When the VPN Is Connected
If the call works without the VPN but drops with it, the VPN is the cause. Check if your VPN has a setting called Force UDP or Enable UDP. Enable it if present. Also try switching the VPN protocol from OpenVPN to IKEv2 or WireGuard, which handle UDP better.
Teams Video Freezes but Audio Continues
This usually indicates high jitter. Jitter is the variation in packet arrival time. The VPN adds jitter. In Teams, go to Settings > Devices and enable Use system audio mode. Also ask your IT team to enable Quality of Service for Teams media on the VPN router.
Teams Shows a Black Screen During Video Calls
A black screen often means the VPN blocks the media ports. Verify that UDP ports 3478 to 3481 are open. Also disable any VPN proxy settings for Teams. In Teams, go to Settings > Network and check the proxy settings. Set them to Use system proxy.
New Teams Desktop vs Teams on the Web for VPN Users
| Item | New Teams Desktop | Teams on the Web |
|---|---|---|
| Media ports | Uses UDP 3478-3481 directly | May fall back to TCP if browser restricts UDP |
| Hardware acceleration | Can be disabled in Settings | Controlled by browser flags |
| VPN split tunneling | Works with most VPN clients | Depends on browser network stack |
| Call reliability | Higher due to native media engine | Lower due to browser limitations |
For the most stable experience over a VPN, use the desktop app. The web client is more likely to drop calls because browsers handle UDP differently.
After applying these changes, test a video call with a colleague. Check the call quality indicator in Teams by selecting the three dots during a call and choosing Call health. Aim for a packet loss below 1 percent and a jitter under 30 milliseconds. If drops continue, contact your IT team to verify the firewall rules and VPN split tunnel configuration. As a final tip, use the Teams network assessment tool to test the connection before important calls.