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  1. I have a few questions around subnetting:

    • My understanding is that networks were broken into classes. This was inefficient. So CIDR was released to allow for “subnet” bits to be browed from the host and additional networks to be created. Is my understanding correct?
    • When subnetting do we always start from the default mask. i.e for a Class A network do I always start with a /8 and then subnet from there?
    • VLSM then allowed for these subnetworks to be variable in length rather then all being the same size. Is my understanding correct?
    • One confusion I have is arou
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  2. Hello Rick

    You got most of it, but I hope this clarifies it a bit more.

    CIDR is Classless Inter Domain Routing. This feature allows routing to occur not only between classful addresses but also between classless addresses. Classless addresses are those that allow a variable length subnet mask (VLSM), those that have a subnet mask other than the allowed classful address. So VLSM is the feature of IP addresses that allows CIDR to take place.

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  3. Hello Rick

    It all depends on what the requirements are. Remember that subnetting is something that you end up applying to a real world network so the network range you start off with can be anything. If you are given a network of and you are asked to further subnet it to segments of /26 then that is what you will do. There is no rule that sa

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  4. Hello Rick

    Yes you’re right. Let me say it another way. The network defines a range of IP addresses from to This is a single subnet with a subnet mask of If you started off with a range of (which is the full range of private class C addresses), and you want to separate this range into /24 subnets, then this means that you can have up to 256 networks with 256 addresses (254 without network and broadcast) in each. In other words, the networks would be:

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