There is a lot of discussion on the forums about passing parameters to an SSRS report using an URL however one of the items that you rarely read about is the passing of multi valued parameters in an URL.
To do this, just pass the name/value pair, separated by the ampersand.
An actual example:
I made a very basic report that displays the actual Parameter Value that was fed to the report and split it with my MultiValue-function for use in a table:
Available Values set for the @MultiParam:
The URL I’m going to use to select two values out of the five default values: