Subnet Mask Dotted Notation

Description	Dotted Notation	Binary Pattern
Class A
Default Mask	255.0.0.0	11111111 00000000 00000000 00000000
1 subnet bit	255.128.0.0	11111111 10000000 00000000 00000000
2 subnet bits	255.192.0.0	11111111 11000000 00000000 00000000
3 subnet bits	255.224.0.0	11111111 11100000 00000000 00000000
4 subnet bits	255.240.0.0	11111111 11110000 00000000 00000000
5 subnet bits	255.248.0.0	11111111 11111000 00000000 00000000
6 subnet bits	255.252.0.0	11111111 11111100 00000000 00000000
7 subnet bits	255.254.0.0	11111111 11111110 00000000 00000000
8 subnet bits	255.255.0.0	11111111 11111111 00000000 00000000
9 subnet bits	255.255.128.0	11111111 11111111 10000000 00000000
10 subnet bits	255.255.192.0	11111111 11111111 11000000 00000000
11 subnet bits	255.255.224.0	11111111 11111111 11100000 00000000
12 subnet bits	255.255.240.0	11111111 11111111 11110000 00000000
13 subnet bits	255.255.248 0	11111111 11111111 11111000 00000000
14 subnet bits	255.255.252.0	11111111 11111111 11111100 00000000
15 subnet bits	255.255.254.0	11111111 11111111 11111110 00000000
16 subnet bits	255.255.255.0	11111111 11111111 11111111 00000000
17 subnet bits	255.255.255.128	11111111 11111111 11111111 10000000
18 subnet bits	255.255.255.192	11111111 11111111 11111111 11000000
19 subnet bits	255.255.255.224	11111111 11111111 11111111 11100000
20 subnet bits	255.255.255.240	11111111 11111111 11111111 11110000
21 subnet bits	255.255.255.248	11111111 11111111 11111111 11111000
22 subnet bits	255.255.255.252	11111111 11111111 11111111 11111100
Class B
Default Mask	255.255.0.0	11111111 11111111 00000000 00000000
1 subnet bit	255.255.128.0	11111111 11111111 10000000 00000000
2 subnet bits	255.255.192.0	11111111 11111111 11000000 00000000
3 subnet bits	255.255.224.0	11111111 11111111 11100000 00000000
4 subnet bits	255.255.240.0	11111111 11111111 11110000 00000000
5 subnet bits	255.255.248.0	11111111 11111111 11111000 00000000
6 subnet bits	255.255.252.0	11111111 11111111 11111100 00000000
7 subnet bits	255.255.254.0	11111111 11111111 11111110 00000000
8 subnet bits	255.255.255.0	11111111 11111111 11111111 00000000
9 subnet bits	255.255.255.128	11111111 11111111 11111111 10000000
10 subnet bits	255.255.255.192	11111111 11111111 11111111 11000000
11 subnet bits	255.255.255.224	11111111 11111111 11111111 11100000
12 subnet bits	255.255.255.240	11111111 11111111 11111111 11110000
13 subnet bits	255.255.255.248	11111111 11111111 11111111 11111000
14 subnet bits	255.255.255.252	11111111 11111111 11111111 11111100
Class C
Default subnet mask	255.255.255.0	11111111 11111111 11111111 00000000
1 subnet bit	255.255.255.128	11111111 11111111 11111111 10000000
2 subnet bits	255.255.255.192	11111111 11111111 11111111 11000000
3 subnet bits	255.255.255.224	11111111 11111111 11111111 11100000
4 subnet bits	255.255.255.240	11111111 11111111 11111111 11110000
5 subnet bits	255.255.255.248	11111111 11111111 11111111 11111000
6 subnet bits	255.255.255.252	11111111 11111111 11111111 11111100