How to create persistence based on semicolon-parameter in URL?

Hello, We have multiple SAP Webdynpro applications integrated into our portal and need to make sure that all are forwarded to the same node based on SAP's URL parameter sap-ext-sid.

 

The URLs look like this: .../sap/app1;sap-ext-sid=aaaaaaaaaaaaaaaaaaaaaa--bbbbbbbbbbbbbbbbbbbbbb-- .../sap/app2;sap-ext-sid=aaaaaaaaaaaaaaaaaaaaaa--cccccccccccccccccccccc--

 

The relevant part are the first 24 characters of sap-ext-sid (aaaaaaaaaaaaaaaaaaaaaa--) which are identical for this user session.

 

How can we make sure that those two requests are forwarded to the same node?

 

Thank you!