Test-Connectivity fails for address *.cdn.office.net, getting name resolution failed

Nazeer, Shalomon 25

Microsoft has announced an update to the global endpoint for the automatic update of the Remote Desktop Client application, with the new address being *.cdn.office.net. However, when testing the connectivity via PowerShell, an error is encountered, indicating "WARNING: Name resolution of *.cdn.office.net failed."

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Robin Hansson 0 Reputation points

2024-12-12T07:42:57.47+00:00

I also have the same question regarding the *.cdn.office.net warning we received today.

I have checked the IP list for both Azure and M365 and none of them contains the endpoint cdn.office.net so can't find which IP to ping since it is not a valid FQDN.
Prrudram-MSFT 27,246 Reputation points

2024-12-12T11:08:40.9633333+00:00

Hello @Nazeer, Shalomon
Which document are you referring to? Please share the link if possible. Also please confirm if you are using RDP client to connect to AVD VMs?
Nazeer, Shalomon 25 Reputation points

2024-12-12T11:14:34.9466667+00:00

@Prrudram-MSFT

Please refer the below URL, yes we use RDP client to connect to AVD VMs
https://learn.microsoft.com/en-us/azure/virtual-desktop/required-fqdn-endpoint?tabs=azure#end-user-devices
Nazeer, Shalomon 25 Reputation points

2024-12-12T11:16:19.05+00:00

https://learn.microsoft.com/en-us/azure/virtual-desktop/required-fqdn-endpoint?tabs=azure#end-user-devices
Robin Hansson 0 Reputation points

2024-12-12T13:54:08.0166667+00:00

I have now spent the majority of the day dealing with this issue and I've used the following methods to come to a conclusion if any actions are neccesary.

I used Microsoft Defender advanced hunting to query for any traffic to the cdn.office.net domain and could find alot of traffic specifically regarding Office products from our computers that were successfull.
I also did the same query specifically for our AVD and got the same result, connections to the domain cdn.office.net have been successfull.

With this information I've come to the very likely conclusion that no problems will be encountered by this update.

If you need the query to check this in advanced hunting here it is:

DeviceNetworkEvents
| where DeviceName contains "<devicename>"
| where RemoteUrl contains "cdn.office.net"

You can remove the line with DeviceName if you want to search all your devices

If anyone has more concrete information about this it would for sure be appreciated, and I will be following the thread the next couple of days since I could be wrong.
Prrudram-MSFT 27,246 Reputation points

2024-12-13T04:58:13.77+00:00

Hi @Nazeer, Shalomon

This is expected as you can't resolve a *.xxx FQDN

If you for e.g. use uci.cdn.office.net, you would be able to resolve it (this is just an example)
Mehabooba M R 0 Reputation points

2024-12-23T04:28:02.65+00:00
I tried the below

Run powershell then run the following commands

$RDAgent = Get-WmiObject -Class Win32_Product | ? Name -eq "Remote Desktop Services Infrastructure Agent" | Sort-Object Version -Descending $path = ($RDAgent[0]).InstallSource + "RDAgent_" + ($RDAgent[0]).Version

cd $path

.\WVDAgentUrlTool.exe

Test-NetConnection -ComputerName "uci.cdn.office.net" -Port 443

Test-NetConnection -ComputerName "cdn.office.net" -Port 443

Test-NetConnection -ComputerName "officecdn.akadns.net" -Port 443
Resolve-DnsName -Name "officecdn.akadns.net"

All the above test failed with either no such host name error , unable to resolve DNS or timeout error.

On running the WVDAgent url tool I didnt find the endpoint *.cdn.office.net in neither in accessible enpoint nor in not accessible endpoint
Does this means the endpoint is blocked ?
what are the other ways I can check ?

How to whitelist the enpoint?

1 answer

Prrudram-MSFT 27,246 Reputation points

2024-12-15T20:35:33.75+00:00

Hello @Nazeer, Shalomon

As mentioned earlier in my comments, the failure in the Test-netconnection is expected as you can't resolve a *.xxx FQDN

If you for e.g. use uci.cdn.office.net, you would be able to resolve it (this is just an example).
As suggested by Robin, if you look at the traffic to the cdn.office.net FQDN, you will see the completely URLs that it communicate to. If *.cdn.office.net is already whitelisted from your network you are good with it. There is nothing to worry about it for now.
If you have any more questions or need further clarification, feel free to ask! 😊

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