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Linux® Routing by Ron McCarty, Dee-Ann LeBlanc, Joe Brockmeier

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Classless IPv4 Addressing

While many of the tenets of IP v4 addressing apply here, such as there being 32 bits in an address divided into four bytes, separated by dots, the new concept you need to become familiar with is Classless Interdomain Routing (CIDR). This subset of IP v4 adds such words to our vocabularies as supernetting and Variable Length Subnet Masks (VLSM). So, buckle your seatbelts—it’s going to be a fun ride.

Differences Between Classful and Classless IPv4 Addressing

There is no class A, B, and so on in CIDR IP v4. No, this does not cause chaos. Instead, all xxx.xxx.xxx.xxx (decimal) combinations come in turn with a bit mask (also called a prefix length). While this item is utilized in IP v4 as a shortcut instead of typing out ...

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