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2

The consensus after discussing with the esteemed forum members is that the link subnets (subnets between two routers) are wasteful: since there are only two devices on the interface, there is no need to have a /16 or /24 subnet. A key concept I was missing was: to denote hierarchy and break the network down into smaller divisions progressively, it is not ...


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This is not a direct answer to the question, but judging from the comments, I think there is a confusion between address aggregation and address assignment. update: i think you can think of this in terms of disjoint sets and set unions. Each subnet is a set of IP addresses. All subnets must be disjoint, that is each subnet is unique. Hierarchy works on ...


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They are "currently unused". On a link where there will never be many nodes, one would never use a /16. Even a /24 would be wasting >90% of the space. It's common practice to use /30 (or /31 if the hardware supports it) for point-to-point links. (Personally, I've used /28 and /29 internally for "device" networks, but your needs may ...


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Each IP address must be unique, no matter what its local subnet mask is or what prefix size is used on a route. Let us say, one address in our subnet is 10.0.0.1 (subnet mask /8) If you use 10.0.0.0/8 on any interface you can use addresses from that subnet only on that segment and nowhere else in your network. Now, we decide to create a subnet further, ...


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I think you might be confusing route aggregation and actual subnet usage. where R1 is a part of a 10.0.0.0/8 network (subnets are indicated by ovals), and it further splits the network into several /16 networks, This will not work (without fine tuning). When 10.0.0.0/8 is used on one interface, that includes all of the subnets as well. (from comment) The ...


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Yes this is wasteful. The remaining IP addresses are lost. This is why we usually configure a /31 on such link. (Well actually if this /16 subnet is not announced to the other routers, technically it could be used somewhere else, but this would be a very dirty configuration).


3

Network classes are long dead, obsoleted in 1993 by CIDR, before the Internet went commercial. You should dump any book on IP from before that year. Classful networking may be interesting for historical reasons but it's completely irrelevant in practical use today. For a private network, just use any subnet(s) from the RFC 1918 ranges 192.168.0.0/16, 172.16....


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For hosts on one network to talk to another network, you require a gateway/router in between and the hosts to have (default) routes that point directly or indirectly to the remote network. You can have all hosts use their local router as default gateway, interconnect the routers and set up a static route on each router for the remote network. Alternatively, ...


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