I have three warehouses A, B and C. Warehouse C is supplied from stock A or B (routes A->C and B->C).

The product XXX has two suppliers ABC and DEF.
Supplier ABC is near the warehouse A.
Supplier DEF is near the warehouse B.

How define routes and suppliers priority?

Now, if I set on product higher priority for supplier DEF and higher priority for route A->C,
purchase order is created and directed to supplier DEF with delivery to the warehouse A (and I would like to B!).