Nt2640 Unit 1

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Unit 1 IP Addresses Classes and Special-Use IP Address Space Network IDs used to be divided into classes, and these classes are Class A, B, and C. These classes were allowed to have a range of addresses depending subnet we are using. This class-based system would work well for a while, but with the rapid growth of the Internet it became evident that this addressing scheme had to be changed in order to support the many networks that were being created (CompTIA Network, Ch.7, 2009). This 32-bit IP addressing system is subdivided into two portions: the network address space and the host address space in IPv4. Class A were created for a very large network with few logical network segments and many hosts that have the high-order bit set to zero. The first octet (the left-most eight bits) is used to define the network ID. Class A address cannot be greater than 127 because a value of 128 would require the left-most bit be set to 1 (CompTIA Network, Ch.7, 2009). Class B always have the first two high-order bits that are set to 10 and are used for medium-sized networks that have a moderate number of hosts connected to them. The Class B network ID, will utilize the first two octets for the network ID, which allows more network IDs and fewer hosts than a Class A network, because it uses an additional octet for the network. Classes C is for small networks with few hosts. These addresses have the first three high-order bits set to 110, because Class C addresses use the first three octets for the network ID and the last octet for the host ID. Class D is reserved for IP multicast addresses. The first four high-order bits are set to 1110. The remaining 28 bits are used for individual IP multicast addresses (Shimonski & Alpern, 2009). RFC 1918 is a standard that reserves several addresses within each of the classes A, B, and C and are commonly used for home,

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