Network Classes

The first step in making plans for IP addressing your community is to decide which community magnificence is suitable for your community. After you’ve got carried out this, you may take the essential 2d step: reap the community variety from the Inter NIC addressing authority.

Currently, there are 3 lessons in TCP/IP networks. Each magnificence makes use of the 32-bit IP deal with the area differently, presenting extra or fewer bits for the community as part of the deal. These lessons are magnificence A, magnificence B, and sophistication C.

Class A Network Numbers

A magnificence A community variety makes use of the primary 8 bits of the IP deal with as its “community part.” The ultimate 24 bits include the host a part of the IP deal with, as illustrated in Figure three-2 below.

The values assigned to the primary byte of sophistication A community numbers fall with inside the variety 0-127. Consider the IP deal with seventy-five.four.10.four. The price of seventy-five with inside the first byte suggests that the host is in a category A community. The ultimate bytes, four.10.four, set up the host deal with. The InterNIC assigns simplest the primary byte of a category A variety. Use of the ultimate 3 bytes is left to the discretion of the proprietor of the community variety. Only 127 magnificence A networks can exist. Each of these sorts of numbers can accommodate as many as sixteen,777,214 hosts.

Class B Network Numbers

A magnificence B community variety makes use of sixteen bits for the community variety and sixteen bits for host numbers. The first byte of a category B community variety is withinside the variety 128-191. In the variety, the primary bytes, 129.144, are assigned via way of means of the InterNIC and include the community deal with. The remaining bytes, 50.56, make up the host deal with and are assigned at the discretion of the proprietor of the community variety. Figure three-three graphically illustrates a category B deal.

Class B is normally assigned to companies with many hosts on their networks.

Class C Network Numbers

Class C community numbers use 24 bits for the community variety and eight bits for host numbers. Class C community numbers are suitable for networks with few hosts–the most being 254. A magnificence C community variety occupies the primary 3 bytes of an IP deal. Only the fourth byte is assigned at the discretion of the community owners. Figure three-four graphically represents the bytes in a category C deal with.

The first byte of a category C community variety covers the variety 192-223. The 2d and 0.33 every cowl the variety 1- 255. A traditional magnificence C deal with is probably The first 3 bytes, 192.5.2, shape the community variety. The very last byte in this example, 5, is the host variety.

Administering Network Numbers

If your company has been assigned a couple of community-wide varieties or makes use of subnets, hire a centralized authority inside your company to assign community numbers. That authority needs to keep manipulating a pool of assigned community numbers, assigning community, subnet, and host numbers as required. To save you problems, make certain that replica or random community numbers do now no longer exist in your company.

Designing Your IP Addressing Scheme

After you’ve got acquired your community-wide variety, you may then plan how you may assign the host elements of the IP to cope with.

suggests the department of the IP cope with the area into a community and host cope with spaces. For every magnificence, “variety” specifies the variety of decimal values for the primary byte of the community-wide variety. “Network cope with” shows the wide variety of bytes of the IP cope with which are devoted to the community a part of the cope with, with every byte represented through xxx. “Host cope with” shows the wide variety of bytes devoted to the host as a part of the cope with. For example, in a category, A community copes with, the primary byte is devoted to the community, and the ultimate 3 are devoted to the host. The contrary is real for a category C community.

Table 1 Division of IP Address Space

Class            Range                                Network Address                          Host Address

A                  zero-127                                      xxx                                  

B                  128-191                                                           

C                  192-223                                                                  xxx

The numbers with inside the first byte of the IP cope with outline whether or not the community is magnificence A, B, or C and are usually assigned through the InterNIC. The ultimate 3 bytes have a variety from zero-255. The numbers zero and 255 are reserved; you may assign the numbers 1-254 to every byte relying upon the community-wide variety assigned to you.

Table 2 suggests which bytes of the IP cope with are assigned to you and the variety of numbers inside every byte which are to be had as a way to assign for your hosts.

Table 2 Range of Available Numbers

Network Class                  Byte Range

A         zero-127          1-254   1-254  1-254

B         128-191           Preassigned through the Internet       1-254   1-254

C         192-223           Preassigned through Internet Preassigned through the Internet             1-254