An issue has been identified which can sometimes affect cloud console users from seeing Chromebook thumbnails from within the Google Chrome browser. If our STUN/TURN servers are accessible from within your network (see here) this issue should not affect you. In some cases, however, this change can be required to view live screens of Chromebooks.
Please note this is not an issue with the software and will be affecting anyone using the WebRTC communication protocol.
Cause: Google introduced a setting within the Chrome browser (starting with Chrome update 75) which is designed to hide the local IP address used within WebRTC by using a technology called mDNS.
From investigations, mDNS queries on certain networks may not have been enabled. This prevents the thumbnails from appearing within the console user’s Chrome browser.
Please make sure that you have whitelisted the STUN and TURN Servers from the following guide
Impero Education Pro Minimum System Requirements for Installation
Resolutions: There are currently two resolutions available that are necessary to be applied to both Teachers & Students devices/networks:
1. Enable mDNS throughout your internal network including wireless controllers.
A quick way on windows (or any device with a chrome browser) to determine which subnet’s mDNS services are visible is to use this tool in the browser:
You can also check this between VLANs using Wireshark using an mDNS query.
2. Configure the following group policy from Google: URLs for which local IPs are exposed in WebRTC ICE candidates.
*This step can be carried out to the local group policy per machine or pushed out from your domain controller to affect all users.
Step 1) Download and extract the latest Chrome ADM templates here: https://support.google.com/chrome/a/answer/187202?hl=en
Step 2) In your desired group policy, OR local group policy, load the Chrome template:
Click on the 'Add' button and navigate to the .ADM file you extracted:
Step 3) Close the window, and navigate to the newly added Chrome settings:
User/Computer Configuration > Administrative Templates > Classic Administrative Templates (ADM) > Google > Google Chrome > URLs for which local IPs are exposed in WebRTC ICE candidates
By default, this setting is set to 'Not configured'. Right-click this setting, and click on 'Edit'.
Set the setting to 'Enabled'. Click the 'Show' button, and add *edpro.cloud* to the list. If you use Classroom Cloud, add *imperosoftware.com* instead. The wildcards here are important.
Click on 'OK' and then on 'Apply'. The group policy is now configured.
If you have applied this to the local group policy, you can test it right away. Otherwise, perform a group policy update from a command prompt (gpupdate /force).
ChromeOS (User Settings) - Google Console
For ChromeOS Devices it is necessary that you enable the below user policy using Google Admin:
Restart Chrome, navigate to chrome://policy and click on the 'Reload policies' button.
If the policy has worked, you should see the following setting in the list, displaying one of the domains you configured previously:
Finally, confirm that the live screens are visible in the cloud console.
Troubleshooting WebRTC Connections;
To check that the Student or Staff device can contact the STUN Servers, you can run this URL on the device - https://webrtc.github.io/samples/src/content/peerconnection/trickle-ice/
When clicking the gather candidates button this should have 2 entries with one of them being the Public IP Address of the network there behind
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