Thanks for the clarification on my sloppy use of the word “couple”. I meant only a limited number, but I did forget what it actually calculated to, and got lazy. FR is amazing in that nothing ever slips by!
However, let me get picky with you. Your statement “that is the only purpose for the mask” is correct from the viewpoint of the operation of the local device. However, from the viewpoint of setting up and designing local networks, the mask is used to establish the overall architecture. Do I have one network, or do I have multiple networks connected by routers? And when you go beyond one network the mask is essential in implementing the design.
Your question borders on the kinds of things I am trying to find out.
I sit at a DOS prompt and type “PING A.B.C.D”
The machine I’m on does not have A.B.C.D in his routing table.
Does my machine just hand it to the gateway? I don’t think so. Somehow, he does something with this magical “mask”.
What? What exactly? And how does the result affect what he does with the packet?
I need a freakin flowchart...