Web Chaining Rules allow you to chain downstream ISA firewalls to upstream ISA firewalls, or even non-ISA firewall-based Web proxy servers. Web proxy chaining allows you to configure a hierarchical caching solution. In contrast, a multi-server ISA firewall array allows you to create a parallel caching solution. You can combine hierarchical and parallel caching solutions to significantly improve performance and reduce the total amount of bandwidth used on Internet links, WAN links, and even on the intranet.
The most popular use for Web Chaining is to chain branch office ISA firewalls with main office ISA firewalls.
To create a Web Chaining Rule, click the Networks node in the left pane of the ISA firewall console and then click the Web Chaining Rules tab in the middle pane. Then perform the following steps to create the Web Chaining Rule:
1. Click the Tasks tab in the Task Pane and then click the Create New Web Chaining Rule link.
2. On the Welcome to the New Web Chaining Rule Wizard page, enter a name for the rule in the Web chaining rule name text box.
3. On the Web Chaining Rule Destination page, click the Add button. In the Add Network Entities dialog box, select the destinations to which this Web Chaining Rule will apply. Since we want all requests for Web content regardless of where that Web content is located to be forwarded to the main office array, we’ll select the All Networks (and Local Host) entry in the Add Network Entities dialog box. Click Close in the Add Network Entities dialog box and then click Next.
4. On the Request Action page, you configure how you want the Web requests to that particular destination routed by the ISA firewall. The default setting is to route the request directly to the destination Web site. However, in a Web Chaining configuration, you want the request forwarded to another Web proxy device. In this case, you would select the Redirect requests to the specified upstream server option. When you select this option, the next page of the wizard will ask you for details regarding the upstream Web proxy. Select this option and click Next.
5. On the Primary Routing page, enter the name of the upstream ISA firewall array. You can leave the default ports in place if you haven’t changed them on the upstream array. Click Next on the Primary Routing page.
6. On the Backup Action page you select how Web requests are routed when the upstream ISA firewall Web proxy . Click Next .