How to Completely Disable ‘Local Network Discovery’ (mDNS) via Group Policy in Microsoft Edge

Local Network Discovery in modern web browsers relies on protocols like Multicast DNS (mDNS) and WebRTC to detect and communicate with devices on the same local area network (LAN), such as smart TVs, casting receivers (Chromecast), or localized IoT devices. While this enables seamless media casting and localized hardware interaction in consumer environments, mDNS broadcasting and local IP address leakage constitute a critical operational security (OPSEC) liability in strict enterprise, military, or zero-trust deployment environments. An unvetted web application executing inside the browser sandbox can abuse these discovery protocols to map the internal network topology, identify localized hardware assets, or establish covert communication channels that bypass the corporate firewall and proxy infrastructure.

This guide explains how to completely disable ‘Local Network Discovery’ (specifically mDNS routing) via Group Policy in Microsoft Edge, enforcing a strict zero-trust model where the browser is cryptographically prevented from mapping or interacting with the local LAN.

Disable Local Network Discovery (mDNS) via Group Policy

To enforce a strict block that permanently neutralizes mDNS and localized WebRTC routing within the browser rendering engine, we must deploy administrative templates. Note that this requires Windows 11 Pro, Enterprise, or Education editions.

1. Log into Windows 11 with an Administrator account.
2. Press the Windows Key + R to open the Run dialogue box.
3. Type gpedit.msc and press Enter to launch the Local Group Policy Editor.
4. In the left-hand navigation pane, strictly follow this exact path:

   Computer Configuration > Administrative Templates > Microsoft Edge

5. In the right-hand pane, locate the policy named Enable multicast DNS (mDNS) (or Allow WebRTC to route over mDNS depending on the specific ADMX template version).
6. Double-click the policy to open its configuration window.
7. Select the radio button next to Disabled. (By explicitly disabling this policy, we instruct the Edge rendering engine and the underlying Chromium network stack to permanently sever its ability to broadcast or receive mDNS packets on the local subnet).
8. Optional but recommended: Locate the policy Anonymize local IPs exposed by WebRTC and set it to Enabled to further prevent internal IP leakage.
9. Click Apply, then click OK.

Verify the Configuration Lockdown

Group Policy changes require the browser to read the registry upon its next launch.

Close all active instances of Microsoft Edge. To force the policy update immediately across the OS, open Command Prompt as Administrator and run gpupdate /force. To verify the restriction is active, launch Microsoft Edge and navigate to edge://policy. Ensure the EnableMulticastDns policy is listed and its value is set to false. Furthermore, attempting to use the “Cast” feature or utilizing a web application that relies on local WebRTC discovery will now fail to identify any devices on the local subnet. The browser is now cryptographically bound to a strict, WAN-only routing state, completely blinding it to the internal corporate LAN topology.