ccna routing cost

ccna routing cost.Authentication Objective 6.026.2 SubnettingOne of the problems with primitive IP addressing is the poor address utilization of Class A and Class B networks. In other words, how many hosts can be contained within a network segment or broadcast domain? Even with the introduction of VLANs, this number has not increased significantly. When using IP, a single broadcast domain can contain 200 ~ 500 devices, and any more than that and you have broadcast problems. This is comparable to the number of host addresses contained in one or two Class C networks. If a single Class B network is assigned to a broadcast domain, more than 65,000 addresses will be wasted.To solve this address waste problem, subnetting was introduced. Subnetting allows you to use the first few host bits to create more networks, so that each network will contain fewer host addresses. These smaller networks are often referred to as subnets. One disadvantage of subnetting is that there will be more addresses unavailable because each subnet has a network address and a directed broadcast address. However, the advantage of subnetting is that the addresses in a classified network can be used more efficiently.Let's look at an example. class C networks have 8 host bits, providing a total of 256 addresses. Of these 256 addresses, only 254 are available for host devices, such as PCs, routers, and servers. Suppose the first host bit is used to create more networks, leaving 7 bits to represent host addresses; this creates two subnets: 2 1 = 2 (where 1 is the number of subnet bits). Each subnet has 126 host addresses: 27.2 = 126. before subnetting, two addresses are unavailable for Class C networks, and after subnetting into two subnets, a total of 4 addresses are unavailable. However, the advantage of this subnetting is that there are now two rather than one networks!Suppose your network has two network segments with 100 hosts in each segment. You could assign a Class C network to each segment, but the addresses would be used extremely inefficiently. By dividing the subnets, you can use the addresses more efficiently. In this example, you can assign only one Class C network and use one subnet bit to divide the subnets, creating two subnets that both contain 126 host addresses. Fewer addresses will be wasted this way.6.2.1 Subnet masksThe Layer 3 addressing scheme is unique to TCP/IP. TCP/IP addresses actually consist of three components: the network part, the host part, and the subnet mask. The subnet mask is used to determine network addresses, host addresses, and directed broadcast addresses. Subnet divisions were originally defined in RFC950.Like IP addresses, the subnet mask is 32 bits in length. When expressed in binary, a 1 in the subnet mask indicates that the corresponding address bit belongs to the network portion, and a 0 indicates that the corresponding address bit belongs to the host portion. One restriction on the subnet mask is that all network bits (1) must be together and all host bits (0) must be together, and this restriction applies not only to a single byte but also to all four bytes o 11110000.00001111.1111111.11111111 (240.31.255.255) is not a valid subnet mask, because the 1's in it are not together. However, 11111111111.11111111.111111111.11111000 ( 255.255.255.248 ) is a valid subnet mask.There are actually four ways to represent a subnet mask, and these are illustrated below using a Class C network as an example.