Table 3-1 shows the division of the IP address space into network and host address spaces. Designing Your IP Addressing SchemeĪfter you have received your network number, you can then plan how you will assign the host parts of the IP address. To prevent problems, make sure that duplicate or random network numbers do not exist in your organization. That authority should maintain control of a pool of assigned network numbers, assigning network, subnet, and host numbers as required.

If your organization has been assigned more than one network number, or uses subnets, appoint a centralized authority within your organization to assign network numbers. The final byte in this example, 5, is the host number. The first three bytes, 192.5.2, form the network number. A typical class C address might be 192.5.2.5. The second and third each cover the range 1- 255. The first byte of a class C network number covers the range 192-223. Figure 3-4 Byte Assignment in a Class C Address Figure 3-4 graphically represents the bytes in a class C address. Only the fourth byte is assigned at the discretion of the network owners. A class C network number occupies the first three bytes of an IP address. Class C network numbers are appropriate for networks with few hosts-the maximum being 254. Class C Network NumbersĬlass C network numbers use 24 bits for the network number and 8 bits for host numbers. Figure 3-3 Byte Assignment in a Class B AddressĬlass B is typically assigned to organizations with many hosts on their networks. Figure 3-3 graphically illustrates a class B address.

The last two bytes, 50.56, make up the host address, and are assigned at the discretion of the owner of the network number. In the number 129.144.50.56, the first two bytes, 129.144, are assigned by the InterNIC, and comprise the network address. The first byte of a class B network number is in the range 128-191. Class B Network NumbersĪ class B network number uses 16 bits for the network number and 16 bits for host numbers. Each one of these numbers can accommodate up to 16,777,214 hosts. Use of the remaining three bytes is left to the discretion of the owner of the network number. The InterNIC assigns only the first byte of a class A number. The remaining bytes, 4.10.4, establish the host address. The value 75 in the first byte indicates that the host is on a class A network. The values assigned to the first byte of class A network numbers fall within the range 0-127. Figure 3-2 Byte Assignment in a Class A Address Class A Network NumbersĪ class A network number uses the first eight bits of the IP address as its 'network part.' The remaining 24 bits comprise the host part of the IP address, as illustrated in Figure 3-2 below. These classes are class A, class B, and class C. Each class uses the 32-bit IP address space differently, providing more or fewer bits for the network part of the address. After you have done this, you can take the crucial second step: obtain the network number from the InterNIC addressing authority.Ĭurrently there are three classes of TCP/IP networks. The first step in planning for IP addressing on your network is to determine which network class is appropriate for your network.

Classful subnetting chart