An interface must be configured with IP 10.10.10.145 and the mask 11111111.11111111.11111111.11111000. Which CIDR prefix should be used?
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Correct answer: /29.
Why this is the answer
The CIDR prefix represents the number of consecutive '1' bits in the subnet mask, starting from the left. The given subnet mask is 11111111.11111111.11111111.11111000. Counting the '1' bits: the first three octets are all '1's, which is 8 bits per octet, totaling 24 bits (8+8+8). The last octet is 11111000, which has five '1' bits. Adding these together (24 + 5) gives a total of 29 '1' bits. Therefore, the correct CIDR prefix is /29. Incorrect options: /30 would mean 30 '1' bits, which corresponds to a mask of 11111111.11111111.11111111.11111100. /27 would mean 27 '1' bits, which corresponds to a mask of 11111111.11111111.11111111.11100000. /28 would mean 28 '1' bits, which corresponds to a mask of 11111111.11111111.11111111.11110000.
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