ccna rs cn sba-b - ospf

ccna rs cn sba-b - ospf.the remaining 3 steps, the subnet mask can be converted to a dotted decimal representation; see Tables 6.3, 6.4, and 6.5 if you need help. however, this conversion is not difficult. First, subnet masks, like IP addresses, can also be expressed in dotted decimal, where each byte is 8 bits. This means that for Class C networks, the first 24 bits of the subnet mask are 1.In other words, the subnet mask is prefixed with 255.255.255. Your task is to determine the value of the last byte of the subnet mask. In this wordsection, the first 4 bits are used to divide the subnet, so simply add up the decimal values corresponding to these bits: 128 + 64 + 32 + 16 = 240.A shortcut can also be used (I always use it). In this example, the host bits used are the rightmost 4 bits, and the decimal values corresponding to these bits are added together: 1 + 2 + 4 + 8 = 15. The maximum value that can be represented by one byte is 255. Since the last 4 bits are not part of the network, the value of the last byte in the subnet mask is obtained by simply subtracting 255 from the value calculated earlier: 255 - 15 = 240. I found it easier to add the smaller values and subtract 255 to get the sum than to add the larger values. Once you become familiar with IP addressing and subnetting, you won't need to use this math trick. Back to our example, the subnet mask for network 192.168.1.0 is 255.255.255.240 (/28).Keep in mind this shortcut for converting a binary subnet mask to dotted decimal format: add the decimal values corresponding to the individual host bits and subtract 255 from the calculated sum.6.3.4 Step 4: Determining the Network AddressIn this step, the subnet created using the new subnet mask needs to be determined. Since IP addressing uses binary, the subnet address is always a multiple of some value; this can be used when determining which subnets a Class C network contains. Don't forget that in the network number, all host bits are 0oIn fact, you already know which value is a multiple of which. This was calculated in step 2 using the formula 2 H -2> =14. 14 is the number of host addresses available for the subnet, but this is not the full number of addresses for the subnet. The subnet also contains network addresses and broadcast addresses, which is the reason for subtracting 2 from the previous formula (because these addresses cannot be used for host devices). Thus, in this example, each subnet has 16 addresses, so the numbering of adjacent subnets differs by 16.You can use another method to verify this. In one byte, the value that can be represented is 0.255, for a total of 256 numbers. To perform the verification described earlier, subtract 256 from the decimal value of the relevant byte in the subnet mask. The relevant byte is the byte where the boundary between the network part and the host part is located, which in this example is the 4th byte. Use this trick: 256 - 240 = 16o Comparing this number with the number obtained earlier will determine that the math operation performed earlier is correct.After determining which value is a multiple, list out the first subnet number and keep adding 16 to the relevant field. table 6.6 lists the network numbers for the subnets contained in network 192.168.1.0. In this table, notice that the last subnet number (192.168.1.240) is more interesting in that the value of its last byte is the same as the value of the relevant byte of the subnet mask, which is 240. This is always the case when you perform subnet segmentation.