INTRODUCTION
When you configure the TCP/IP protocol on a Microsoft Windows computer, an IP address, subnet mask, and usually a default gateway are required in the TCP/IP configuration settings.
To configure TCP/IP correctly, it is necessary to understand how TCP/IP networks are addressed and divided into networks and subnetworks. This article is intended as a general introduction to the concepts of IP networks and subnetting. A glossary is included at the end of article.
MORE INFORMATION
The success of TCP/IP as the network protocol of the Internet is largely because of its ability to connect together networks of different sizes and systems of different types. These networks are arbitrarily defined into three main classes (along with a few others) that have predefined sizes, each of which can be divided into smaller subnetworks by system administrators. A subnet mask is used to divide an IP address into two parts. One part identifies the host (computer), the other part identifies the network to which it belongs. To better understand how IP addresses and subnet masks work, look at an IP (Internet Protocol) address and see how it is organized.
IP addresses: Networks and hosts
An IP address is a 32-bit number that uniquely identifies a host (computer or other device, such as a printer or router) on a TCP/IP network.
IP addresses are normally expressed in dotted-decimal format, with four numbers separated by periods, such as 192.168.123.132. To understand how subnet masks are used to distinguish between hosts, networks, and subnetworks, examine an IP address in binary notation.
For example, the dotted-decimal IP address 192.168.123.132 is (in binary notation) the 32 bit number 110000000101000111101110000100. This number may be hard to make sense of, so divide it into four parts of eight binary digits.
These eight bit sections are known as octets. The example IP address, then, becomes 11000000.10101000.01111011.10000100. This number only makes a little more sense, so for most uses, convert the binary address into dotted-decimal format (192.168.123.132). The decimal numbers separated by periods are the octets converted from binary to decimal notation.
For a TCP/IP wide area network (WAN) to work efficiently as a collection of networks, the routers that pass packets of data between networks do not know the exact location of a host for which a packet of information is destined. Routers only know what network the host is a member of and use information stored in their route table to determine how to get the packet to the destination host’s network. After the packet is delivered to the destination’s network, the packet is delivered to the appropriate host.
For this process to work, an IP address has two parts. The first part of an IP address is used as a network address, the last part as a host address. If you take the example 192.168.123.132 and divide it into these two parts you get the following:
192.168.123. Network
.132 Host
-or-
192.168.123.0 - network address.
0.0.0.132 - host address.
简介
在 Microsoft Windows 计算机上配置 TCP/IP 协议时，TCP/IP 配置设置中需要 IP 地址和子网掩码，通常还需要一个默认网关。
要正确配置 TCP/IP，有必要了解 TCP/IP 网络的寻址方式以及网络和子网的划分方式。本文旨在对 IP 网络和子网的概念进行一般性介绍。本文结尾包含一个术语表。
更多信息
作为 Internet 的网络协议，TCP/IP 的成功在很大程度上归功于它将不同大小的网络和不同类型的系统连接在一起的能力。这些网络被强制定义为具有预定义大小的三个主要类（还有其他一些类别），每一类都可以由系统管理员分成更小的子网。子网掩码用于将 IP 地址分成两个部分。一部分标识主机（计算机），另一部分标识它所属的网络。查看 IP（Internet 协议）地址并研究它的组织方式可以帮助您更好地理解 IP 地址和子网掩码的工作方式。
IP 地址：网络和主机
IP 地址是一个 32 位数字，它唯一地标识 TCP/IP 网络上的主机（计算机或其他设备，如打印机或路由器）。
IP 地址通常以点分十进制格式表示，四个数字由句点分隔，例如 192.168.123.132。要了解子网掩码如何用于区分不同的主机、网络和子网，请查看以二进制表示的 IP 地址。
例如，点分十进制 IP 地址 192.168.123.132 在二进制表示法中为 32 位数字 110000000101000111101110000100。此数字的含义可能很难理解，因此它被分成四个部分，每个部分有八个二进制数字。
这些八位部分称为八位组。示例 IP 地址于是变成 11000000.10101000.01111011.10000100。此数字表示的含义只是稍微明白了一点，因此在大多数应用中，会将二进制地址转换为点分十进制格式 (192.168.123.132)。点分十进制数字是从二进制转换为十进制表示法的八位组。
为了让 TCP/IP 广域网 (WAN) 以一个网络集的形式高效工作，在网络间传递数据包的路由器并不知道信息包的目标主机的确切位置。路由器只知道主机是哪一个网络的成员，并使用存储在路由表中的信息来确定如何将数据包送达目标主机的网络。当数据包被传送到目标网络后，该数据包就会被传送到相应的主机。
为了让此过程顺利进行，IP 地址分为两个部分。IP 地址的前一部分作为网络地址，后一部分作为主机地址。以 192.168.123.132 为例，将它分为这两个部分之后，会得到：
192.168.123. 网络
.132 主机
- 或 -
192.168.123.0 — 网络地址。
0.0.0.132 — 主机地址。
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