The Cyber Mentor's Subnetting Sheet
CIDR
Hosts
/1
2,147,483,648
/2
1,073,741,824
/3
536,870,912
CIDR
Hosts
/9
8,388,608
/10
4,194,304
/11
2,097,152
CIDR
Hosts
/17
32,768
/18
16,384
/19
8,192
CIDR
Hosts
/25
/26
/27
Subnet Mask (Replace x)
128
128
Notes:
Hosts
Subnet
64
192
32
Subnet x.0.0.0
/4
268,435,456
Subnet 255.x.0.0
/12
1,048,576
Subnet 255.255.x.0
/20
4,096
Subnet 255.255.255.x
/28
16
224
240
*Hosts double each increment of a CIDR
*Always subtract 2 from host total:
Network ID - First Address
Broadcast - Last Address
1
9
17
25
2
10
18
26
3
11
19
27
4
12
20
28
5
13
21
29
128
128
64
192
32
224
16
240
8
248
Subnetting Sheet
Subnet x.0.0.0
/5
134,217,728
Subnet 255.x.0.0
/13
524,288
Subnet 255.255.x.0
/21
2,048
Subnet 255.255.255.x
/29
8
/6
67,108,864
/7
33,554,432
/8
16,777,216
/14
262,144
/15
131,072
/16
65,536
/22
/23
/24
1,024
/30
512
/31
4
256
/32
2
248
252
254
6
14
22
30
7
15
23
31
8
16
24
32
4
252
2
254
1
255
1
255