Welcome to Brendon Davis

ISA doesn’t support Kerberose Auth

Autor brendon

For web proxy request, ISA only supports Basic or NTLM authentication. Some knowledgebase articles with more information are KB322822 and KB239869.

IE7 now supports Kerberos authentication to web servers however under certain circumstances it has been known to forward credentials to ISA 2004/ 2006 using Kerberos instead of NTLM. The symptoms are that when accessing sites through the proxy, it will repeatedly prompt you for domain username and password.

As a work around, to override this behaviour Under Tools -> Internet Options -> Advanced, towards the bottom of the page, disable the tick box for ‘Enable Integrated Authentication’ and restart IE.

More Information:
http://support.microsoft.com/kb/239869
http://support.microsoft.com/kb/322822
http://forums.isaserver.org/m_2002033963/mpage_1/key_/tm.htm#2002033963