There are four octet in IPV4. Each octet has 8 bits. So, there are 32 bits in IPV4. IPV4 is based on binary (0, 1) and decimal (0 to 9).
1st Octet 2nd Octet 3rd Octet 4th Octet
8 bits 8 bit 8 bits 8 bits
27 26 25 24 23 22 21 20 27 26 25 24 23 22 21 20 27 26 25 24 23 22 21 20 27 26 25 24 23 22 21 20
255.255.255.255 255.255.255.255 255.255.255.255 255.255.255.255
How to become 255.255.255.255 ? As each octet has 8 bit and is based on binary....
27 = 128, 26 = 64, 25 = 32, 24 = 16, 23 = 8, 22 = 4, 21 = 2, 20 = 1
128 + 64 + 32 + 16 + 8 + 4 + 2 + 1 = 255
Let's try to change from the Decimal to the Binary....
Decmial Binary
1st Octet 2nd Octet 3rd Octet 4th Octet 1st Octet 2nd Octet 3rd Octet 4th Octet
192 . 168 . 1 . 0 = 11000000 . 10101000 . 00000001 . 00000000
223 . 200 . 100 . 25 = 11011111 . 11001000 . 01100100 . 00011001
172 . 16 . 31 . 87 = 10101100 . 00010000 . 00011111 . 01010111
Let's explore 192.168.1.0/24....
1st Octet 2nd Octet 3rd Octet 4th Octet
8 bits 8 bit 8 bits 8 bits
27 26 25 24 23 22 21 20 27 26 25 24 23 22 21 20 27 26 25 24 23 22 21 20 27 26 25 24 23 22 21 20
255.255.255.255 255.255.255.255 255.255.255.255 255.255.255.255
Network Host
Network Address = 192.168.1.0
Subnet Mask = 255.255.255.0
Usable IP Addresses = 192.168.1.1 to 192.168.1.254
Broadcast Address = 192.168.1.255
Let's explore 192.168.1.0/25....
1st Octet 2nd Octet 3rd Octet 4th Octet
8 bits 8 bit 8 bits 8 bits
27 26 25 24 23 22 21 20 27 26 25 24 23 22 21 20 27 26 25 24 23 22 21 20 27 26 25 24 23 22 21 20
255.255.255.255 255.255.255.255 255.255.255.255 255.255.255.255
Network Host
1st Network Address = 192.168.1.0
Subnet Mask = 255.255.255.128
Usable IP Addresses = 192.168.1.1 to 192.168.1.126
Broadcast Address = 192.168.1.127
2nd Network Address = 192.168.1.128
Subnet Mask = 255.255.255.128
Usable IP Addresses = 192.168.1.129 to 192.168.1.254
Broadcast Address = 192.168.1.255
Let's explore 192.168.1.0/26....
1st Octet 2nd Octet 3rd Octet 4th Octet
8 bits 8 bit 8 bits 8 bits
27 26 25 24 23 22 21 20 27 26 25 24 23 22 21 20 27 26 25 24 23 22 21 20 27 26 25 24 23 22 21 20
255.255.255.255 255.255.255.255 255.255.255.255 255.255.255.255
Network Host
1st Network Address = 192.168.1.0
Subnet Mask = 192.168.1.192
Usable IP Addresses = 192.168.1.1 to 192.168.1.62
Broadcast Address = 192.168.1.63
2nd Network Address = 192.168.1.64
Subnet Mask = 192.168.1.192
Usable IP Addresses = 192.168.1.65 to 192.168.1.126
Broadcast Address = 192.168.1.127
3rd Network Address = 192.168.1.128
Subnet Mask = 192.168.1.192
Usable IP Addresses = 192.168.1.129 to 192.168.1.190
Broadcast Address = 192.168.1.191
4th Network Address = 192.168.1.192
Subnet Mask = 192.168.1.192
Usable IP Addresses = 192.168.1.193 to 192.168.1.254
Broadcast Address = 192.168.1.255
(Note: The Subnet Mask is reverse proportional to host range. The larger the subnet mask, the smaller the host range.)
The following table is formula for Ipv4 addresses (Class C). I've made it when I was in Singapore Polytechnic.
Binary Decimal Prefix Subnet Mask Count of Networks Usable Ip Range
- - /24 255.255.255.0 1 254
27 128 /25 255.255.255.128 2 126
+
26 64 /26 255.255.255.192 4 62
+
25 32 /27 255.255.255.224 8 30
+
24 16 /28 255.255.255.240 16 14
+
23 8 /29 255.255.255.248 32 6
+
22 4 /30 255.255.255.252 64 2
