Which of the following are valid subnet masks for a Class B

Which of the following are valid subnet masks for a Class B address space?

A. 255.254.0.0

B. 255.255.0.0

C. 255.255.245.0

D. 255.255.254.0

E. 255.255.192.224

Solution

B and D are correct. 255.255.0.0 is the default subnet mask for a Class B address space, and 255.255.254.0 is a valid subnet mask.

A, C, and E are incorrect. A is not correct because 255.254.0.0 will not work because it is smaller than the default mask for a Class B address. C is not correct because 255.255.245.0 will not work because 245 is not allowed (it is not a consecutive series of 1s) within a subnet mask. E is not correct because 255.255.192.224 is incorrect because the subnet mask must always be a series of consecutive 1s from left to right.