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comptia a practice exams as decimal 255. Consequently, the subnet mask in the example can be denoted in two ways, as shown in Figure 2.7. (The spaces in the above example are only for illustrative purposes. The subnet mask in decimal would actually appear as 255.255.255.0.) Not all networks need to have subnets and therefore don’t need to use custom subnet masks. In this case, they are said to have a default subnet mask. This is basically the same as saying they don’t have a subnet address. Table 2.4 shows the default subnet masks for the different classes of networks. Once the network administrator has created the subnet mask and assigned it to each machine, the IP software applies the subnet mask to the IP address to determine its subnet address. The word mask carries the implied meaning of “lens” in this case—the IP software looks at its IP address through the lens of its subnet mask to see its subnet address. Figure 2.8 illustrates an IP address being viewed through a subnet mask. In this example, the IP software learns through the subnet mask that, instead of being part of the host address, the third byte of its IP address is a practice exams now going to be used as a subnet address. The IP software then looks in its IP address at the bit positions that correspond to the mask, which are 0000 0001. The final step is for the subnet bit values to be matched up with the binary numbering convention and converted to decimal. In the Widget, Inc., example, the binary-to-decimal conversion is simple, as illustrated in Figure 2.9. By using the entire third byte of a Class B address as the subnet address, it is easy to set and determine the subnet address. For example, if Widget, Inc., wants to have a subnet 6, the third byte of all machines on that subnet will be 0000 0110 (decimal 6 in binary). ">Hence, those bit positions are represented with 1s in the subnet mask. The fourth byte is the only part of the example that represents the host address. The subnet mask can also be expressed using the decimal equivalents of the binary patterns. The binary pattern of 1111 1111 is the same comptia a practice exams as decimal 255. Consequently, the subnet mask in the example can be denoted in two ways, as shown in Figure 2.7. (The spaces in the above example are only for illustrative purposes. The subnet mask in decimal would actually appear as 255.255.255.0.) Not all networks need to have subnets and therefore don’t need to use custom subnet masks. In this case, they are said to have a default subnet mask. This is basically the same as saying they don’t have a subnet address. Table 2.4 shows the default subnet masks for the different classes of networks. Once the network administrator has created the subnet mask and assigned it to each machine, the IP software applies the subnet mask to the IP address to determine its subnet address. The word mask carries the implied meaning of “lens” in this case—the IP software looks at its IP address through the lens of its subnet mask to see its subnet address. Figure 2.8 illustrates an IP address being viewed through a subnet mask. In this example, the IP software learns through the subnet mask that, instead of being part of the host address, the third byte of its IP address is a practice exams now going to be used as a subnet address. The IP software then looks in its IP address at the bit positions that correspond to the mask, which are 0000 0001. The final step is for the subnet bit values to be matched up with the binary numbering convention and converted to decimal. In the Widget, Inc., example, the binary-to-decimal conversion is simple, as illustrated in Figure 2.9. By using the entire third byte of a Class B address as the subnet address, it is easy to set and determine the subnet address. For example, if Widget, Inc., wants to have a subnet 6, the third byte of all machines on that subnet will be 0000 0110 (decimal 6 in binary).
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