The idea of order routing has been scoped a lot of times when speaking to users who can't move forward with Dear because they have multiple warehouses and the allocation of stock is done according to the costing method.
The proposal/idea to overcome this is to create some sort of logic/priority allocation of stock based on location (certain states/countries should have stock allocated from a specific warehouse) or order of preference (i.e. Warehouse 1, then Warehouse 2, etc.).
A common scenario is, for US, a West coast and East coast warehouse and depending on the state where the customer is located/shipped will default to it's correct warehouse/location. Same goes for different countries.
The second scenario would be by priority. Such as, all the time, if stock is available, it should be allocated from the Main Warehouse but if there should be no stock it should then be allocated from Location 2.
Please check article explaining how DEAR order routing works http://support.dearsystems.com/a/solutions/articles/11000057238