Solution
If your network uses proxy servers to access the Internet, one of the following methods should help avoid internet access issues for AutoCAD components:
Exception Rules:
If you are experiencing issue accessing Autodesk servers through a proxy, adding an exception to the Internet Explorer proxy settings to allow the following domains to bypass the proxy server should help:
*.autodesk.com
*.google-analytics.com
*.cloudfront.net
Note: Please make sure your network is setup to route requests directly to the these domains without routing through the proxy servers.

Authenticated Proxies:
To use the above mentioned AutoCAD Online components through proxy servers with Authentication enabled, you should enable http (port 80) and https (port 443) access to the following domains in the proxy without Proxy Authentication (i.e. Access for “All users” or Anonymous access through the proxy):
*.autodesk.com
*.google-analytics.com
*.cloudfront.net
Transparent proxies:
An intercepting proxy (also known as a forced proxy or transparent proxy) combines a proxy server with a gateway or router (commonly with NAT capabilities). Connections made by client browsers through the gateway are diverted to the proxy without client-side configuration (or, often, knowledge). Connections may also be diverted from a SOCKS server or other circuit-level proxies.
Transparent proxies will not prevent access to Autodesk Server components.
Related questions & answers:
Q: Why can’t we use IP addresses for the firewall rules?
A: The Single Sign-On solution from Autodesk takes advantage of Akamai for network route optimization. Because the Akamai network has many (1000s) of edge nodes which change over time, it is not advisable to filter based on IP addresses. If filtering is required, then it should be done by URL (*.autodesk.com).
Q: Why should we enable special rules in the proxy server for certain URLs?
A: AutoCAD currently does not send authentication information to the proxy server; hence an exception rule is required on the proxy to enable these communications anonymously.
Q:What if we don’t use proxy servers and access the control list directly on the firewall?
A: If the rules can be added with DNS names you could use the above mentioned URLs to allow the traffic.
Q:We have secureNAT on our clients why I can’t I access any of Autodesk 360 services?
A: The issue is due to the ISA Firewall service performing reverse DNS name resolution to determine whether a rule applies for every request from SecureNAT client. If you add Akamai hosts (*. edgekey.net & *.akamaiedge.net) to the exception lists this should resolve the issue.
Support – Terms of UseAUTODESK DOES NOT GUARANTEE THAT YOU WILL BE ABLE TO SUCCESSFULLY DOWNLOAD OR IMPLEMENT ANY SERVICE PACK OR WORKAROUND, OR ANY OF THE TIPS, TRICKS, EXAMPLES OR SUGGESTIONS OUTLINED IN ANY AUTODESK PRODUCT SUPPORT TECHNICAL DOCUMENTS. TECHNICAL DOCUMENTS, SERVICE PACKS AND WORKAROUNDS ARE SUBJECT TO CHANGE WITHOUT NOTICE TO YOU. AUTODESK PROVIDES TECHNICAL DOCUMENTS, SERVICE PACKS AND WORKAROUNDS "AS IS" WITHOUT WARRANTY OF ANY KIND, WHETHER EXPRESS OR IMPLIED, INCLUDING WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL AUTODESK OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF DATA, OR LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, THAT MAY OCCUR AS A RESULT OF IMPLEMENTING ANY SERVICE PACK OR WORKAROUND, OR ANY SUGGESTION OUTLINED IN ANY AUTODESK PRODUCT SUPPORT TECHNICAL DOCUMENT, EVEN IF AUTODESK OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.