Package manager in Visual Studio 2015 "407 (Proxy Authentication Required)"

I had to modify the 32 bit machine.config (assumption being VS runs in 32 bit) to add the <system.net> section but omitting anything within the <defaultProxy> tag:

<system.net>
    <defaultProxy useDefaultCredentials="True" enabled="True" />
</system.net>

According to MSDN:

If the defaultProxy element is empty, the proxy settings from Internet Explorer will be used.

This is perfect for me as every other application on my machine works - including IE.

manchine.config location (Win 7): %SYSTEMROOT%\Microsoft.NET\Framework\v4.0.30319\Config\machine.config

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Note

I resolved this thanks to @user3063127 pointing me in the right direction (you have an upvote). As far as I can tell this only affects package restore on DNX projects and may well be fixed when RC2 is released.

I had the same problem a few weeks ago. For me it has helped to put in the the following in the machine.config (Windows/Microsoft.NET/Framework64/v4.0.30319/Config)

<system.net>
   <settings>
       <ipv6 enabled="True"/>
   </settings>
   <defaultProxy useDefaultCredentials="True" enabled="True">
       <proxy proxyaddress="http://your.proxyserver.ip:port"/>
   </defaultProxy>
</system.net>