Since LoadMaster version 188.8.131.52, it is possible to copy header values into a new header name. The value can be dynamic because the LoadMaster copies any value into the new header.
A good use case scenario is as follows; the LoadMaster can inject the X-Forwarded-For header. This header copies the originating client IP address and places it as the value for the X-Forwarded-For header. Your server might need to see the originating client IP address but will only take that value from a custom header. The LoadMaster takes the value of the X-Forwarded-For header, copies it, and then places that value into the new custom header. Both headers are sent to the Real Server. An example is below.
In this Virtual Service there is an additional header of X-Forwarded-For.
In the TCP dump below, you can see that I connect to the Virtual Service of 10.1.112.63 with an IP address of 10.0.11.209.
In the back-end connection, the LoadMaster injects the IP address of 10.0.11.209 into the X-Forwarded-For header into the HEAD request sent to the Real Server.
If we go back to the LoadMaster Virtual Service and use the Copy Header in Request feature, we will see our new header with the same value as the X-Forwarded-For value in the HEAD request.