【導(dǎo)讀】大小的網(wǎng)絡(luò)和不同類型的系統(tǒng)連接在一起的能力。這些網(wǎng)絡(luò)被強(qiáng)制定義為具有預(yù)。子網(wǎng)掩碼用于將IP地址分成兩個(gè)部分。另一部分標(biāo)識(shí)它所屬的網(wǎng)絡(luò)。查看IP地址并研究它的組織方。式可以幫助您更好地理解IP地址和子網(wǎng)掩碼的工作方式。中需要IP地址和子網(wǎng)掩碼，通常還需要一個(gè)默認(rèn)網(wǎng)關(guān)。有必要了解TCP/IP網(wǎng)絡(luò)的尋址方式以及網(wǎng)絡(luò)和子網(wǎng)的劃分方式。IP網(wǎng)絡(luò)和子網(wǎng)的概念進(jìn)行一般性介紹。本文結(jié)尾包含一個(gè)術(shù)語表。制格式表示，四個(gè)數(shù)字由句點(diǎn)分隔，例如。這些八位部分稱為八位組。點(diǎn)分十進(jìn)制數(shù)字是從二進(jìn)制轉(zhuǎn)換為十進(jìn)制表示法的八位組。它的主要責(zé)任是確保端至端之。IP位于下一層，在OSI的網(wǎng)絡(luò)層，即第三層，把每個(gè)包的發(fā)送。TCP/IP在整個(gè)房間或圍繞地球進(jìn)行傳遞。每個(gè)包攜帶一個(gè)源地址，在目前規(guī)范下，包長(zhǎng)度是32位。每個(gè)包也攜帶最終目的地的IP地址。該路由器檢查包的。網(wǎng)廣播一個(gè)ARP請(qǐng)求，擁有此IP地址的端站就作出響應(yīng)，把MAC地址發(fā)送回去，子網(wǎng)掩碼是TCP/IP正常工作所必需的。

　　

【正文】 er whether the destination is a local host or a remote host. If the result of this process determines the destination to be a local host, then the puter will simply send the packet on the local sub. If the result of the parison determines the destination to be a remote host, then the puter will forward the packet to the default gateway defined in its TCP/IP properties. It is then the responsibility of the router to forward the packet to the correct sub. XXII Seven) Troubleshooting TCP/IP work problems are often caused by incorrect configuration of the three main entries in a puter39。s TCP/IP properties. By understanding how errors in TCP/IP configuration affect work operations, you can solve many mon TCP/IP problems. Incorrect Sub Mask: If a work uses a sub mask other than the default mask for its address class, and a client is still configured with the default sub mask for the address class, munication will fail to some nearby works but not to distant ones. As an example, if you create four subs (such as in the subting example) but use the incorrect sub mask of in your TCP/IP configuration, hosts will not be able to determine that some puters are on different subs than their own. When this happens, packets destined for hosts on d ifferent physical works that are part of the same Class C address will not be sent to a default gateway for delivery. A mon symptom of this is when a puter can municate with hosts that are on its local work and can talk to all remote works except those that are nearby and have the same class A, B, or C address. To fix this problem, just enter the correct sub mask in the TCP/IP configuration for that host. Incorrect IP Address: If you put puters with IP addresses that should be on separate subs on a local work with each other, they will not be able to municate. They will try to send packets to each other through a router that will not be able to forward them correctly. A symptom of this problem is a puter that can talk to hosts on remote works, but cannot municate with some or all puters on their local work. To correct this problem, make sure all puters on the same physical work have IP addresses on the same IP sub. If you run out of IP addresses on a single work segment, there are solutions that go beyond the XXIII scope of this article. Incorrect Default Gateway: A puter configured with an incorrect default gateway will be able to municate with hosts on its own work segment, but will fail to municate with hosts on some or all remote works. If a single physical work has more than one router, and the wrong router is configured as a default gateway, a host will be able to municate with some remote works, but not others. This problem is mon if an anization has a router to an internal TCP/IP work and another router connected to the Inter. XXIV Eight) Reference Two popular references on TCP/IP are: TCP/IP Illustrated, Volume 1: The Protocols, Richard Stevens, Addison Wesley, 1994 Interworking with TCP/IP, Volume 1:Principles Protocols, and Architecture, Douglas E. Comer, Prentice Hall,1995 It is strongly remended that a system administrator responsible for TCP/IP works have at least one of these references available. XXV Nine) Glossary Broadcast address An IP address with a host portion that is all ones. Host A puter or other device on a TCP/IP work. Inter The global collection of works that are connected together and share a mon range of IP addresses. InterNIC The anization responsible for administration of IP addresses on the Inter. IP The work protocol used for sending work packets over a TCP/IP work or the Inter. IP Address A unique 32bit address for a host on a TCP/IP work or interwork. Network There are two uses of the term work in this article. One is a group of puters on a single physical work segment。 the other is an IP work address range that is allocated by a system administrator. Network address An IP address with a host portion that is all zeros. Octet An 8bit number, 4 of which prise a 32bit IP address. They have a range of 0000000011111111 that correspond to the decimal values 0 255. Packet A unit of data passed over a TCP/IP work or wide area work. RFC (Request for Comment) A document used to define standards on the Inter. Router A device that passes work traffic between different IP works. Sub Mask A 32bit number used to distinguish the work and host portions of an IP address. Sub or Subwork A smaller work created by dividing a larger work into equal parts. TCP/IP Used broadly, the set of protocols, standards and utilities monly XXVI used on the Inter and large works. Wide area work (WAN) A large work that is a collection of smaller works separated by routers. The Inter is an example of a very large WAN.