How the Picking Route ID is generated for sales order


We are migrating from AX 2009 to AX 2012. During this process we found that our AX 2009 system use to generate multiple picking route id if there are multiple sales order lines each with different warehouse. But this is not working in AX 2012, System always generates single picking route id regardless of different warehouse in each sales line. I am not sure if this functionality is changed in AX 2012 or is there any configuration setting which will enable this in AX 2012.

This is very urgent for the client. As i am new to AX i could not figure this out and need your help at the earliest. Any help here is appriciated