Which configuration command must be in effect to allow the use of 8 subnets if the Class C subnet mask is 255.255.255.224?
A. Router (config) #ip classless
B. Router (config) #no ip classful
C. Router (config) #ip unnumbered
D. Router (config) #ip subnet-zero
Answer: Option D
Solution (By Examveda Team)
A Class C subnet mask of 255.255.255.224 is 3 bits on and 5 bits off (11100000) and provides 8 subnets, each with 30 hosts. However, if the commandip subnet-zero is not used, then only 6 subnets would be available for use. 

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