I regularly connect to an external website which uses IIS's Integrated Windows authentication (aka NTLM). When connecting to this site via a modem and dial-up account, IE6 prompts for a username and password. But when using the LAN connection, via a PIX 501, there is no prompt for credentials and the server returns HTTP 401.2 immediately.
Interestingly, if I set up the website to listen on port 8001 (or whatever) as well as 80, then it works fine through the PIX as well as the dial-up.
Can anyone shed any light on this? Thanks.