Unable to install .NET Framework 3.5 feature in Azure Windows Server images

Windows Azure provides images of Windows Server 2008 and 2012. Using a few mouseclicks a new virtual machine can be depoyed in just minutes.

Just like when using your own Windows install, if you need .NET Framework 3.5 you will need to install this feature. It is listed in the ‘Add roles and features’ wizard.

In Windows Azure you might get the error listed below:

Installation of one or more roles, role services, or features failed. The source files could not be found.

dotnetinstall-fail

You will get the following error if the conditions listed below are valid:

1. the virtual machine is part of an Azure Virtual Network

2. DNS server(s) are added to the Azure Virtual Network configuration

3. Those DNS server do not have a forward to an external DNS server able to resolve internet based servers.

Cause of issue

For installing .NET 3.5,  Windows Server needs to download binaries located on an internet server. Probably located at microsoft.com.

If your Azure virtual machine is not part of a virtual network, it will be configured with a Microsoft managed DNS server by DHCP. This DNS server will be able to resolve DNS queries to internet based servers. So download and installation of .NET will be sucesfully.

If the VM is part of a virtual network, and you filled in the DNS server name/IP, you as tenant are responsible for providing DNS.

In the Azure Virtual  Network configuration tab a DNS servername and IP-address can be supplied. Make sure this DNS server is able to resolve internet based servers. If not, download of .NET and thus install will fail.

If you do not manage/have access to  a DNS server, use Google public DNS at 8.8.8.8

Make sure to reboot the VM if you make changes to the Virtual Network configuration. Ipconfig will not result in providing the VM with DNS server details.

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About Marcel van den Berg
I am a technical consultant with a strong focus on server virtualization, desktop virtualization, cloud computing and business continuity/disaster recovery.

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