At work,we have got ISA 2004 (FQDN: proxy.rami.ae,,,,,fake name ) which has two interfaces,

NICA 192.168.1.250 connected to core switch 4500

NICB for DMZ area ,,192.168.101.294

From DMZ through PIX to outside world.

I believe that all internal PCs (workstations) go to internet through ISA, the reason (Is it right conclusion ? ) I am saying that because we have to configure proxy within Internet Explorer -- > Internet Option Connection LAN setting

proxy,,,,,,,,,,,,,,,,,,port 8080

Some times when there is lack in the internet connection , I changed the LAN Setting to :

proxy1.telecomm.net.jp (fake one),,,,,,,,,port 8080

And some times If I chose the option :,,,,,,,,,,,,is this some thing related to a browser cache ?

Automatically detect settings ,,,,it worked as well

How can we troubleshoot (step-by-step) that ? (i.e how can we force in PCs use the right proxy ?)