Which of the following dotted-decimal notation (DDN) is equivalent of /28.

(A) 255.255.255.240
(B) 255.128.224.0
(C) 255.255.255.224
(D) 255.255.255.248 1

255.255.255.240 is the correct answer. The forth octet, 11110000, converts to 240, for a DDN mask of 255.255.255.240.

Binary Mask Octet	Decimal Equivalent	Number of Binary 1s
00000000	0	0
10000000	128	1
11000000	192	2
11100000	224	3
11110000	240	4
11111000	248	5
11111100	252	6
11111110	254	7
11111111	255	8