通信外文翻译了解 TCPIP 寻址和子网配置基础知识Word下载.docx

1、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

2、 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.Back to the top MORE INFORMATIONThe success of TCP/IP as the network protocol of the Internet is largely because of its ability to connect

3、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

4、 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 hostsAn IP ad

5、dress 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

6、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 part

7、s 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

8、 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 de

9、stined. 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 hosts network. After the packet is delivered to the destinations network, the packet is delivered to the appropriate host.For this proc

10、ess 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 addres

11、s.0.0.0.132 - host address. Subnet maskThe second item, which is required for TCP/IP to work, is the subnet mask. The subnet mask is used by the TCP/IP protocol to determine whether a host is on the local subnet or on a remote network.In TCP/IP, the parts of the IP address that are used as the netwo

12、rk and host addresses are not fixed, so the network and host addresses above cannot be determined unless you have more information. This information is supplied in another 32-bit number called a subnet mask. In this example, the subnet mask is 255.255.255.0. It is not obvious what this number means

13、unless you know that 255 in binary notation equals 11111111; so, the subnet mask is: 11111111.11111111.11111111.0000000Lining up the IP address and the subnet mask together, the network and host portions of the address can be separated: 11000000.10101000.01111011.10000100 - IP address （192.168.123.1

14、32） 11111111.11111111.11111111.00000000 - Subnet mask （255.255.255.0）The first 24 bits （the number of ones in the subnet mask） are identified as the network address, with the last 8 bits （the number of remaining zeros in the subnet mask） identified as the host address. This gives you the following:

15、11000000.10101000.01111011.00000000 - Network address （192.168.123.0） 00000000.00000000.00000000.10000100 - Host address （000.000.000.132）So now you know, for this example using a 255.255.255.0 subnet mask, that the network ID is 192.168.123.0, and the host address is 0.0.0.132. When a packet arrive

16、s on the 192.168.123.0 subnet （from the local subnet or a remote network）, and it has a destination address of 192.168.123.132, your computer will receive it from the network and process it.Almost all decimal subnet masks convert to binary numbers that are all ones on the left and all zeros on the righ