I tried to Linux FC5 at work (Active Directory), I have been able to access the net , I have not logged in as with my AD account , I logged in as root and password : forum,,,fake one (I know security implication, I have done for test ).
First time when I tried to open a browser, window popped up asking me username and password for authentication to use internet (I entered my username: zillah and password:ad2003 my active directory account,,,fake ), then I was able to browse the net.

When I tried to use this command (via Terminal):

yum install yum ,,,,It did not work, but unfortunately I did record what was the error message, I believe because of the authentication that I mentioned above.

How can I overcome this issue ?
Does that mean I can not login as stand alone machine within AD environment, unless I have installed samba ?

If yum is already installed then why are you trying to install it?

I was trying to use yumex, therefore i was to install it first

1- First I updarded (not fresh installation) from FC5 to FC6

2- I tried from a shell console as root
[root@localhost ~]# yum update yum
Loading "installonlyn" plugin
Setting up Update Process
Setting up repositories
Could not retrieve mirrorlist http://mirrors.fedoraproject.org/mi...ore-6&arch=i386 error was
[Errno 4] IOError: <urlopen error (-2, 'Name or service not known')>
Error: Cannot find a valid baseurl for repo: core
[root@localhost ~]#