Prior to release of 6.0 SP6 the host header is not available during request processing when WebAgent process an HTTP request. This header is required by the WebAgent because it used to determine agent name, server name and server IP. If the client sent the HTTP 1.1 request, the host header was present in the request but if the client sent the HTTP 0.9/1.0 request, the host header was not present in the request that caused the 500 (Internal Server Error) errors on accessing the protected resource.
HTTP 0.9/1.0 does not support Host Headers, and as such request using this protocol will generate 500 errors on the Agent. With the latest release of SiteMinder WebAgent 6.0SP6 (for 6.x releases) and R12 SP2 CR1 (for R12 releases) a new ACO parameter "DefaultHostName" has been introduced for getting the name of Host if Host header is not present in the HTTP header. Now, for HTTP 1.1 request the host information will be getting from the request headers and for HTTP 0.9/1.0 the host information will be getting from the new ACO parameter "DefaultHostName". This will be available for all the SiteMinder supported Framework WebAgent (IIS6, SunOne and Apache 2.x ...).