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The answer depends on how you obtained IHS.
Under some circumstances, your sales representative may be able to arrange for "standalone support" of IBM HTTP Server, which carries detailed terms and conditions.
When another vendor lists IBM HTTP Server as a "supported webserver", this is a statement of their own support position in terms of interoperability, and has no bearing on entitlement to support with IBM.
Sometimes, people refer to the capability provided by the WAS WebServer Plug-in as "reverse proxy". We're not addressing that here, as it's almost always a supported configuration. This section refers to using mod_proxy with IHS.
The generic proxy support in mod_proxy is never supported as a frontend to WebSphere Application Server. The WebSphere Plugin is the only supported mechanism to connect IHS with WebSphere Application Server.
Some very limited reverse proxy (gateway) usage in such an instance of IHS can be supported, but never in the following cases:
The functionality is not a "direct and necessary" to the licensed use of the IBM product that included IHS.
Colocation of function within a server that has some "direct and necessary" use with some that does not does not obviate this requirement.
The reverse proxy is frontending a non-IBM Application Server (including non-java Application Servers).
Using IHS as a reverse proxy in front of another IHS that meets the support requirements is technically supported, but is not a tested or recommended configuration. IBM support can only provide limited support in such an environment. Customers should consult IBM Services about the best architecture for your requirements, not IBM support.
Forward proxy is not tested, recommended, or believed to meet the functionality/reliability needs of IHS provided with WebSphere Application Server. Products that bundle IHS for use as a forward proxy must test, certify, and tune for their narrow usage. Dedicated proxy servers, or other dedicated network hardware, are strongly recommended in favor of re-purposing IHS to provide additional network connectivity to WebSphere-hosted applications.
An example of a supported reverse proxy usage would be to forward small ranges of the URI-space to another server during a period of migration, or to workaround virtual-host related configuration issues, in a way that complies with all the provisions of this document.
If an IBM product bundles IBM HTTP Server, they may use mod_proxy in their own supported configurations. In this case, the expectation is that the product team narrowly defines, tests, and supports the set of supported configurations.
Some WAS Community Edition (CE) support contracts include support for using IHS w/ mod_proxy, mod_proxy_balancer, and mod_proxy_ajp w/ WAS CE.
One very special case is the IBM API Connect product. It bundles IBM HTTP Server and Liberty ND and allows nodes.js servers to be added to the collective and routed to via dynamic routing (AKA Intelligent Management for WebServers or "ODRLIB").
Finally, customers using Proxy functionality are encouraged to move to IHS 7.0 or later if possible. This is partially due to the higher quality proxy support in Apache 2.2.x and partially due to IHS 7.0 being more recently "rebased" then previous releases.
IHS is supported on any virtualization technology that runs a supported, unmodified, operating system. We assume any usage question or defect report is virtualization-agnostic until evidence shows otherwise, and won't ask customers to recreate an issue natively unless we suspect the problem is unique to the virtualization environment.
Technote #1242532 formally covers the virtualization policy for WebSphere Application Server (including IHS).We don't have any tips for the tuning the guest or hypervisor for IHS.
IHS includes a module, mod_fastcgi, that allows proxying requests to an application that speaks the FastCGI protocol. A typical FastCGI application resembles the combination of a basic (non-websphere) application server environment plus a users own application written to that servers programming model.
A common example is a PHP or Perl application sitting on top of a PHP or Perl web development frameork
This module was originally included in IHS when IHS was developed as a standalone commercial webserver. For many years, IHS has been provided only as a reusable component within IBM products (WebSphere Application Server, for example). When IHS is included this way it is only supported when used in a direct and necessary way for the combined product.
For this reason, mod_fastcgi is generally not part of a supported configuration for products that bundle IHS. Customer and product support are only available for supported configurations. While the interpetation of "direct and necessary" is not always clear, IBM support considers cases where the FastCGI usage is clearly in lieu of using the preferred programming language/model/runtime of the product (such as using PHP for pieces of a web application that would otherwise be implemented in Websphere Application Server)
See #SUPPORTED for more details about how IHS is provided in IBM products, and #PROXY for more information on a similar, but less black-and-white, support issue.