Do you have an Enterprise Portal system that is in front of an SRM system?
Or maybe in front of an ECC?
What about in front of both?!?!
If that was not enough, you still need to configure a single entry point using the SAP Web Dispatcher.
How do you configure all these systems to work together?
Fear not! Read the Web Dispatcher for Multiple Systems – Understanding and Examples - Application Server Infrastructure - SCN Wiki page and start putting all together! 
Feedback on the WIKI is most welcome! You can leave a comment at the WIKI itself, or at this blog post.
Cheers,
Isaías
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