ISA Server provides many important networking functions that include Firewalling, Web-cache, Policy-based Administration, Dynamic IP Filtering, VPN Support, Intrusion Detection, NAT and reporting. While being a robust solution for Windows-based clients, its a pain for Linux users because most of the Linux-based browsers do not appear to be working behind it. The term 'appear to be' is used because there are some known workouts for this.
While running Windows-based clients behind ISA Server, have you noticed that normally you could browse using only Internet Explorer, and not using other browsers like Netscape? This is because ISA server uses an authentication mechanism it calls 'Integrated Authentication.' When Internet Explorer contacts ISA server to request a page, along with every request it sends a hash that the server uses to authenticate you as a legitimate domain user [You can verify this fact by sniffing some packets while you browse, just check the request header that your browser sends to the ISA server]. This authentication method is not supported by other browsers, which is why it renders most of the browsers useless.
The following sections will tell you about two methods to enable your Linux-based browser to browse the net.