Internet Protocol (IP) addresses are the numerical addresses used to identify a particular piece of hardware connected to the Internet. An IP address has two parts: network and host numbers. The network section identifies the specific network and the host section identifies the specific node (E.g., a particular computer).
Today, the two most common versions of IP are Internet Protocol version 4 (IPv4) and Internet Protocol version 6 (IPv6). Both IPv4 and IPv6 addresses come from finite pools of numbers. They are decimal representations of four binary blocks, E.g., 173.208.140.42.
The IPv4 pool has 32-bits (232) in size, whereas the IPv6 address space has 128-bits (2128). The IPv4 pool can be divided into four 8-bit numbers — or octets — separated by a decimal point. These octets range in number from zero to 255.Here's the chart which explains Subnet mask, Assisgned IPs, usable IPv4 etc.
| CIDR | Subnet mask | Wildcard mask | # of IP addresses | # of usable IP addresses |
|---|---|---|---|---|
| /32 | 255.255.255.255 | 0.0.0.0 | 1 | 1 |
| /31 | 255.255.255.254 | 0.0.0.1 | 2 | 2* |
| /30 | 255.255.255.252 | 0.0.0.3 | 4 | 2 |
| /29 | 255.255.255.248 | 0.0.0.7 | 8 | 6 |
| /28 | 255.255.255.240 | 0.0.0.15 | 16 | 14 |
| /27 | 255.255.255.224 | 0.0.0.31 | 32 | 30 |
| /26 | 255.255.255.192 | 0.0.0.63 | 64 | 62 |
| /25 | 255.255.255.128 | 0.0.0.127 | 128 | 126 |
| /24 | 255.255.255.0 | 0.0.0.255 | 256 | 254 |
| /23 | 255.255.254.0 | 0.0.1.255 | 512 | 510 |
| /22 | 255.255.252.0 | 0.0.3.255 | 1,024 | 1,022 |
| /21 | 255.255.248.0 | 0.0.7.255 | 2,048 | 2,046 |
| /20 | 255.255.240.0 | 0.0.15.255 | 4,096 | 4,094 |
| /19 | 255.255.224.0 | 0.0.31.255 | 8,192 | 8,190 |
| /18 | 255.255.192.0 | 0.0.63.255 | 16,384 | 16,382 |
| /17 | 255.255.128.0 | 0.0.127.255 | 32,768 | 32,766 |
| /16 | 255.255.0.0 | 0.0.255.255 | 65,536 | 65,534 |
| /15 | 255.254.0.0 | 0.1.255.255 | 131,072 | 131,070 |
| /14 | 255.252.0.0 | 0.3.255.255 | 262,144 | 262,142 |
| /13 | 255.248.0.0 | 0.7.255.255 | 524,288 | 524,286 |
| /12 | 255.240.0.0 | 0.15.255.255 | 1,048,576 | 1,048,574 |
| /11 | 255.224.0.0 | 0.31.255.255 | 2,097,152 | 2,097,150 |
| /10 | 255.192.0.0 | 0.63.255.255 | 4,194,304 | 4,194,302 |
| /9 | 255.128.0.0 | 0.127.255.255 | 8,388,608 | 8,388,606 |
| /8 | 255.0.0.0 | 0.255.255.255 | 16,777,216 | 16,777,214 |
| /7 | 254.0.0.0 | 1.255.255.255 | 33,554,432 | 33,554,430 |
| /6 | 252.0.0.0 | 3.255.255.255 | 67,108,864 | 67,108,862 |
| /5 | 248.0.0.0 | 7.255.255.255 | 134,217,728 | 134,217,726 |
| /4 | 240.0.0.0 | 15.255.255.255 | 268,435,456 | 268,435,454 |
| /3 | 224.0.0.0 | 31.255.255.255 | 536,870,912 | 536,870,910 |
| /2 | 192.0.0.0 | 63.255.255.255 | 1,073,741,824 | 1,073,741,822 |
| /1 | 128.0.0.0 | 127.255.255.255 | 2,147,483,648 | 2,147,483,646 |
| /0 | 0.0.0.0 | 255.255.255.255 | 4,294,967,296 | 4,294,967,294 |
The IPv4 networks address used classes to identify the number of bytes allocated to the network component. The main classes were class A, B, C. With the allocation is as follows:
Class A network,node,node,node
Class B network,network,node,node
Class C network,network,network,node
Class D and Class E IP Addresses
The last two classes are Class D, and Class E. Class D IP addresses are reserved for multicasts. It ranges from 224.0.0.0 to 239.255.255.255. Class E IP addresses are experimental and over 240.0.0.0.
To determine the class, you needed to examine the most significant byte (far left).
- 0-127 Class A
- 128-191 Class B
- 192-ccc Class C
What is IPv4 Subnetting?
From the above table, we can see that the number of IP addresses is practically unlimited. After all, almost 4.2 billion possible IPv4 addresses are available. Currently, the Internet has grown, and more devices are connected these days, resulting in a shortage of IPv4 addresses.
As this shortage was recognized years ago, developers came up with a way to split up an IP address into smaller networks called subnets.
This process, called subnetting, uses the host section of the IP address to break it down into those smaller networks or subnets.
This is used to free up more IPv4 addresses and segment networks for security & easier management.
What is /24 subnet?
A /24 subnet means that the first 24 bits of the IP address are part of the Network number (191.68.54.0) the last part is part of the host address (1-254). This is called "slash notation". With a /24 subnet, you will be receiving a total of 256 IPs on which 253 IPs are usable.
Uses of 24 subnets and other additional IPv4 subnets:
The IPs can be used for multiple purposes. Mainly an IPv4 is used for:
- Setting a VPN
- To set up an Email Server
For email servers, there are only two major reasons for adding new IP addresses: Volume (as it pertains to time) and having multiple email channels or mail streams.
