Learning about Subnets, but I can't shake a question I have that I think prevents me from fully grasping the concept.

Hello All,

I'm studying to get my Network + certification and have looked up a number of resources on the subject.

I think I understand what subnetting is, but at a certain point I have a difficult time grasping the concept of why someone would need to do it, even on a larger private network. Maybe there's pieces I don't have yet, and I'm hoping maybe someone here can fill those cracks that makes me "get" it.

Lets say we have 192.168.1.0/24

That gives us 254 addresses to use. Now, subnetting this further down to say, 192.168.1.0/25 would give us two groups, 192.168.1.1-192.158.1.126, and 192.168.1.128-192.168.1.254. We have this subnetted, but we don't get to use 192.168.1.127 now.

What benefit does someone have subnetting below 254 hosts? I can't wrap my head around the idea of giving yourself even less IPs than you started with. If the two subnets can intercommunicate, why remove an IP that the network could use (192.168.1.127)? If they can't intercommunicate, why not just use a different Network ID all together and now open yourself to two networks with 254 IPs to use?

I think I can understand on a larger network (Internet) the need for subnetting as a means to allow for more IPs to be accessible to be used (just as so many people CAN use 192.168.0 /24). But once the network reaches the LAN, I just can't seem to make sense of why you would need to.

I feel like there's a critical bit of information that I'm not seeing, or that I haven't somehow come across yet that allows me to understand this better. Something that I couldn't know to think of because I haven't used it or seen it. If someone could provide an example of why subnetting on a smaller network would make sense, I would appreciate it.