Not to be picky but a mask of 255.255.255.248 allows 6 usable addresses....255.255.255.252 would allow for only a couple (2). A subnet mask is used ONLY by the local host (computer, router, whatever) when it has a IP packet to send - it uses the mask to make it’s one routing decision - (1) does this packet have a destination address for devices on my local network - if so it will “flood” out a query packets to all local devices asking “who has this IP address” or (2) this packet is not meant for anyone on my local network and therefore I will send this packet to may default gateway (typically your router). That is the only purpose for the mask - is a packet that I need to send out my interface local or not).....
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.