You can identify the class of an IP address by looking at the first octet of the address. The first octet is the first group of numbers in the IP address, separated by periods.
IP address classes
Class A: 10.0.0.0 to 10.255.255.255
Class B: 172.16.0.0 to 172.31.255.255
Class C: 192.168.0.0 to 192.168.255.255
Class D: 224.0.0.0 to 239.255.255.255
Class E: 240.0.0.0 to 255.255.255.255
|
Class of IP |
Range of First Octet |
|---|---|
|
Class A |
0-127 |
|
Class B |
127-191 |
|
Class C |
192-223 |
|
Class D |
224-239 |
|
Class E |
240-255 |
-
- Class A: The first octet is between 0 and 126. This class is for large networks. (10 popular)
- Class B: The first octet is between 128 and 191. This class is for medium-sized networks. (172 popular)
- Class C: The first octet is between 192 and 223. This class is for small networks. (192.168.0.1) your wifi router address
- Class D: The first octet is between 224 and 239. This class is used for multicast addressing. host
- Class E: The first octet is between 240 and 255. This class is reserved for experimental purposes.
The number of subnets and the number of hosts per subnet differ between the first three classes.
CIDR Range chart
Class A network contains 224(IP addresses) or 224 – 2 Hosts, (network & broad cost ip adresses)
Class B network contains 216(IP addresses) or 216 – 2 Hosts,
Class C network contains 28(IP addresses) or 28 – 2 Hosts
Class B supported 65,534 hosts
Class C supported 254 hosts
| Subnet Mask | CIDR | Total IPs | Usable IPs | Subnet Range Example |
|---|---|---|---|---|
| /32 | 1 | 0 | ||
| 255.255.255.252 | /30 | 4 | 2 | 192.168.1.0 – 192.168.1.3 |
| 255.255.255.248 | /29 | 8 | 6 | 192.168.1.0 – 192.168.1.7 |
| 255.255.255.240 | /28 | 16 | 14 | 192.168.1.0 – 192.168.1.15 |
| 255.255.255.224 | /27 | 32 | 30 | 192.168.1.0 – 192.168.1.31 |
| 255.255.255.192 | /26 | 64 | 62 | 192.168.1.0 – 192.168.1.63 |
| 255.255.255.128 | /25 | 128 | 126 | 192.168.1.0 – 192.168.1.127 |
| 255.255.255.0 | /24 | 256 | 254 | 192.168.1.0 – 192.168.1.255 |
Below is a table providing typical subnets for IPv4 before CIDR.
| Prefix size | Network mask | Usable hosts per subnet |
| /1 | 128.0.0.0 | 2,147,483,646 |
| /2 | 192.0.0.0 | 1,073,741,822 |
| /3 | 224.0.0.0 | 536,870,910 |
| /4 | 240.0.0.0 | 268,435,454 |
| /5 | 248.0.0.0 | 134,217,726 |
| /6 | 252.0.0.0 | 67,108,862 |
| /7 | 254.0.0.0 | 33,554,430 |
| Class A | ||
| /8 | 255.0.0.0 | 16,777,214 |
| /9 | 255.128.0.0 | 8,388,606 |
| /10 | 255.192.0.0 | 4,194,302 |
| /11 | 255.224.0.0 | 2,097,150 |
| /12 | 255.240.0.0 | 1,048,574 |
| /13 | 255.248.0.0 | 524,286 |
| /14 | 255.252.0.0 | 262,142 |
| /15 | 255.254.0.0 | 131,070 |
| Class B | ||
| /16 | 255.255.0.0 | 65,534 |
| /17 | 255.255.128.0 | 32,766 |
| /18 | 255.255.192.0 | 16,382 |
| /19 | 255.255.224.0 | 8,190 |
| /20 | 255.255.240.0 | 4,094 |
| /21 | 255.255.248.0 | 2,046 |
| /22 | 255.255.252.0 | 1,022 |
| /23 | 255.255.254.0 | 510 |
| Class C | ||
| /24 | 255.255.255.0 | 254 |
| /25 | 255.255.255.128 | 126 |
| /26 | 255.255.255.192 | 62 |
| /27 | 255.255.255.224 | 30 |
| /28 | 255.255.255.240 | 14 |
| /29 | 255.255.255.248 | 6 |
| /30 | 255.255.255.252 | 2 |
| /31 | 255.255.255.254 | 0 |
| /32 | 255.255.255.255 | 0 |