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 may be required to view live screens of Chromebooks.


Please note this is not an Impero software created issue 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 will prevent thumbnails from appearing within the console user’s Chrome browser.


Resolutions: There are currently two resolutions available:


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:

https://chrome.google.com/webstore/detail/mdns-browser/kipighjpklofchgbdgclfaoccdlghidp


 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


Windows Devices


*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 the 'Add' button and navigate to the .ADM file you extracted: 

...\GoogleChromeEnterpriseBundle64\Configuration\adm\en-US\chrome.adm



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 '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 'OK' and then 'Apply'. The group policy has now been 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)


For ChromeOS Devices you will need to enable the below user policy using Google Admin:




Restart Chrome, navigate to chrome://policy and click 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.