计算机通信网教案(2008双语)chapter 19 Network Layer Logical Addressing

Chapter 19

Network Layer:

Logical Addressing

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Dotted-Decimal Notation

IPv4 address is usually written in decimal form with a decimal point (dot) separating the bytes. For example:

Note that because each byte is 8 bits, each number in dotted-decimal notation is a value ranging from 0 to 255.

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Figure 19.2 Finding the classes in binary and dotted-decimal notation

The net-id is in yellow, the host-id is in white.

Note that the concept does not apply to classes D and E.

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Example

For example, if the university has 35 departments, instead of having a single class B address with 14 bits for the net-id and 16 bits for the host-id, it could use a 6-bit subnet-id and a 10-bit host-id, allowing for up to 64 Ethernets, each with a maximum of 1022 hosts.

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Subnet Mask

The subnet mask is 32-bit long, the bits for the net-id and subnet-id are all set to 1, and the bits for the host-id are all set to 0.

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Default masks for classful addressing Table 19.2 Default masks for classful addressing

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Example

Supposing a network with the class C network address 202.168.10.0, it is required to be divided 4 subnets, please solve the following problems:

(1) the subnet mask;

(2) the network IP address of each subnet;

(3) the range of host IP address of each subnet ( i.e. write the first host IP address and the last host IP address of each subnet).

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