Captive Portal NTLM Authentication Fails With IE11
After upgrading to Internet Explorer 11 (IE11), NTLM authentication fails and the client is redirected to the web-form.
In IE11 it appears the way intranet sites are detected has been changed. By default, the auto-detect is turned off, among other settings. The change causes the NTLM authentication portal to be identified as an internet resource by the browser. Since NTLM authentication is only allowed by intranet resources, authentication will fail.
A workaround is to open the "Local intranet" zone settings and add the Captive Portal redirect host. This will help identify the redirect page as intranet and trustworthy, and restore NTLM functionality.