Thanks for you reply.
In fact, it is working on different prefix. But if I send my flow (here ICMP but the same for TCP, ...) it will go through the same link. If I apply, for example, all different values of TOS on the flow, the flow still use the same path. Or, according to the documentation, the TOS is used in the hash.
I think something is not clear for me about the way it selects the path according to the packet fields
