Stefan wrote  on Tue, 07 Oct 2008 09:15:21 +0200:

If you login in from that dialog, does it work?

It sounds like you're seeing the IE security settings at work - if there is
a . in the hostname then IE treats the request as being in the "Internet
Zone" and so won't attempt to log in automatically even over NTLM. With no .
(ie data5) the site is treated as being in the "Intranet Zone" so it does
attempt to auto login. If you add data5.domain.local to the "Trusted Sites"
in IE it should autologin - however you will need to push this setting out
to all your users (if you use Group Policy that shouldn't be too hard, but
if you have any machines connecting you don't have control over you'll have
to ask those users to add your server hostname to the Trusted Sites list in
IE).

On Oct 7, 12:15 am, Stefan Mitterbuchner <dr_mitch*NO-SP...@web.de>
wrote:

This is by-design.

By default, IE does not perform auto-login for URLs with FQDN or IP
addresses because they are considered in the "Internet Zone".
Meanwhile, just "data5" is considered "Intranet Zone", which has auto-
login.

To "get around this", you will have to configure the browsers to trust
the FQDN, either by making people add the FQDN to their Trusted Sites
list, or change Internet Zone to auto login.

However, be aware that both are undesirable from a security
perspective because:
- you don't want to auto-login for the Internet Zone (that would be a
security hazard -- a hacker site can use Basic Auth + Auto-Login to
steal your username/password)
- it is a hassle to get users to add FQDN into the Trusted Sites list,
and you don't want users accustomed to adding random FQDN into their
Trusted Sites list just to "make things work".

In general, if you are trying to login from the Internet, you should
provide credentials. If your users are inside the domain and Intranet,
then they should use the Internal name and not FQDN.

In other words, the default settings are for your safety, and when you
alter them for convenience, you are explicitly responsible for the
security of your own choices.

//David
http://w3-4u.blogspot.com
http://blogs.msdn.com/David.Wang
//