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Internal site name in Web farm publishing

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ISA Server 2006 allows you to publish a farm of Web servers that perform the same role, or host the same content. Web farm publishing distributes requests evenly among available farm members, detects offline members, and implements failover. You can drain, remove and add farm members without disrupting current connections. Read more about Web farm publishing at the ISA Server TechCenter. 

When you publish a single Web server, the concept of the internal site name is well understood. It is used by ISA Server to locate the published server. When you use the New Web Publishing Rule wizard to publish a Web farm, the wizard text also seems to suggest this. It states the following: "Specify the internal name of the Web site you are publishing". But when publishing multiple Web servers in a farm, which name should you specify?

Understanding how ISA Server uses the internal site name in Web farm publishing provides some insight:

  • The internal name is used as the host header when connecting to the server farm.
    •  For each Web publishing rule, ISA Server automatically maps the internal name specified in the rule to the public name specified in the rule. A request from a client browser includes a host header with the URL requested by the client. When ISA Server receives the request, by default it changes this host header to the internal site name, and uses this to connect to the Web farm. If you specify in the rule that the original client host header should be used, instead of the default setting, the internal name is not used.
  • The internal name is used if link translation is required:
    • Web pages returned by a published Web server may include links to internal computer names and sites that cannot be resolved by external clients. To avoid broken links, link translation maps these internal links to publicly resolvable names.  
    • If link translation is required, you should specify the internal name with which the Web farm might be referenced on Web pages and e-mail messages that external users may receive. If an application uses absolute links to itself, the internal site name should be the host name in those links.

  • The internal site name is used when publishing a Web farm over HTTPS.

    When you configure a Web farm in an HTTPS-to-HTTPS bridging scenario, you can do either of the following:

    • Deploy a unique certificate on each server farm member, where each certificate name matches the server name.
    • Use a single certificate for the Web farm object. In this case, you must use the internal site name specified in the publishing rule as the common name when creating the certificate.
  • Even if you do not need to make a Web farm available internally or account for link translation, the ISA Server rules engine may need to resolve the internal site name. Use a resolvable DNS name. We recommend that you use the name of one of the servers in the farm.

Rayne Wiselman

ISA Server User Assistance Team

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