Which of the following is the resident subnet for the IP address 187.225.25.48/20?

A) 187.225.48.0
B) 187.225.32.0
C) 187.225.16.0
D) 187.225.0.0

C
Explanation: C) The correct answer is 187.225.16.0 because, first, the resident subnet (the subnet ID of the subnet in which the address resides) must be numerically smaller than the IP address, which rules out two of the answers. The mask converts to 255.255.240.0. As such, you can copy the first two octets of the IP address because of their value, 255. 55. For the third and fourth octet, the subnet ID value must be a multiple of 16 (magic number) because 256 - 240 (mask) = 16. Those multiples include 0 and 16, and the correct choice is the multiple closest to the IP address value in that octet (25.48 ) without going over. So, the correct subnet ID is 187.225.16.0.