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Implementing the Reverse Proxy Filter
Mechanism 
The reverse proxy filter enables the portal to modify HTTP responses to requests that are transmitted via a proxy server, and to respond to multiple domain names.
The filter enables the portal to do the following:
● Modify HTTP responses to requests that are transmitted via a proxy server so that content in the portal that is referenced by absolute URLs becomes available to clients.
● Work with multiple domain names via several proxy servers.
● Use aliases for proxy servers in the portal environment.
However, the reverse proxy filter should only be used as a fallback when no http-header forwarding of name and port can be used. Consider the possibility of limitations with respect to using one portal infrastructure with multiple domain names, certificates, link generation or others.
The filter mechanism for proxy servers is manually configured in the portal landscape.
For information, see the section Implementing the Reverse Proxy Filter Mechanism for the Portal in Configuring the J2EE Engine Deployment Descriptor at SAPService Marketplace, service.sap.com/nw70-howtoguides ® Portal, KM and Collaboration ® Portal.
In addition, the guide describes how to create your own filter mechanism for any proxy server, for example, one that is homegrown, using code samples.