A Class B network needs to be subnetted such that it supports 100 subnets and 100 hosts/subnet. Which of the following answers list a workable combination for the number of network, subnet, and host bits? (Choose two answers.)
- Network = 16, subnet = 7, host = 7
- Network = 16, subnet = 8, host = 8
- Network = 16, subnet = 9, host = 7
- Network = 8, subnet = 7, host = 17
Explanation: At least 7 subnet bits are needed because 26 = 64, so 6 subnet bits could not number 100 different subnets. Seven subnet bits could because 27 = 128 >= 100. Similarly, 6 host bits is not enough because 26 – 2 = 62, but 7 host bits is enough because 27 − 2 = 126 >= 100.
The number of network, subnet, and host bits must total 32 bits, making one of the answers incorrect. The answer with 8 network bits cannot be correct because the question states that a Class B network is used, so the number of network bits must always be 16. The two correct answers have 16 network bits (required because the question states the use of a Class B network) and at least 7 subnet and host bits each.
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