ccna routing practice labs

ccna routing practice labs.10000000 =128 11110000=240 11111110=25411000000 =192 11111000 =248 11111111 =255The default subnet mask for a Class A network is 255.0.0.0: the first byte is the network number and the other three bytes are the host number; the default subnet mask for a Class B network is 255.255.0.0: the first two bytes are the network number and the last two bytes are the host number; the default subnet mask for a Class C network is 255.255.255.0: the first three bytes are the network number and the last byte is the host number.Exam Essentials The subnet mask is invalid whenever numbers not listed in Table 6.2 are used.One important point to note is that the subnet mask itself is meaningless if it is not associated with an IP address. For example, most people think that a subnet mask of 255.255.255.0 means that the corresponding network is a Class C network. However, don't forget that Class A, Class B, and Class C networks can be subnetted, so subnet mask 255.255.255.0 can be used for Class A and Class B networks as well. Thus, there is a symbiotic relationship between IP addresses and subnet masks. The next few subsections describe the subnet masks that can be used for Class A, Class B, and Class C networks.When subnetting, the first subnet and the last subnet (subnet 0) may or may not be available, depending on the device. It is important to keep this in mind when taking the exam, as the questions may or may not indicate whether or not they are available. However, the answers will not be contradictory; they will either contain both the first and last subnets, or neither.2. Subnet masks for Class A networksTable 6.3 lists the valid subnet masks for Class A networks, where the number of network bits is the total number of bits in the network and subnet parts. For a point-to-point link requiring only two host addresses, 255.255.255.252 is the optimal subnet mask.3. Subnet masks for Class B networksTable 6.4 lists the valid subnet masks for Class B networks, where the number of network bits is the total number of bits in the network and subnet parts. It is important to be able to determine how many subnets will be created and how many host addresses each subnet contains based on the address and subnet mask Q