# CIDR Conversion Table

## CIDR Conversion Table

### **Understanding:**

Class A, B, and C Networks:

The above table uses Class A, B, and C to define network types. Network classes define how many addresses are allowed on the network, with class A being the largest and class C being the smallest. Specific size details are defined in the following class definitions:

**Class A:** Allows 224 host addresses on the network. The starting host address is 0.0.0.0 and the ending address is 127.0.0.0. These networks use the 255.0.0.0 subnet mask, or /8 CIDR notation.

**Class B:** Allows 216 host addresses on the network. The starting host address is 128.0.0.0 and the ending address is 191.255.0.0. These networks use the 255.255.0.0 subnet mask, or /16 CIDR notation.

**Class C:** Allows 28 host addresses on the network. The starting host address is 192.0.0.0 and the ending address is 223.255.255.0. These networks use the 255.255.255.0 subnet mask, or /24 CIDR notation.

### **CIDR Conversion Table:**

| CIDR Length | Mask            | # of Networks | #  of Hosts   |
| ----------- | --------------- | ------------- | ------------- |
| /1          | 128.0.0.0       | 128 A         | 2,147,483,392 |
| /2          | 192.0.0.0       | 64 A          | 1,073,741,696 |
| /3          | 224.0.0.0       | 32 A          | 536,870,848   |
| /4          | 240.0.0.0       | 16 A          | 268,435,424   |
| /5          | 248.0.0.0       | 8 A           | 134,217,712   |
| /6          | 252.0.0.0       | 4 A           | 67,108,856    |
| /7          | 254.0.0.0       | 2 A           | 33,554,428    |
| /8          | 255.0.0.0       | 1 A           | 16,777,214    |
| /9          | 255.128.0.0     | 128 B         | 8,388,352     |
| /10         | 255.192.0.0     | 64 B          | 4,194,176     |
| /11         | 255.224.0.0     | 32 B          | 2,097,088     |
| /12         | 255.240.0.0     | 16 B          | 1,048,544     |
| /13         | 255.248.0.0     | 8 B           | 524,272       |
| /14         | 255.252.0.0     | 4 B           | 262,136       |
| /15         | 255.254.0.0     | 2 B           | 131,068       |
| /16         | 255.255.0.0     | 1 B           | 65,024        |
| /17         | 255.255.128.0   | 128 C         | 32,512        |
| /18         | 255.255.192.0   | 64 C          | 16,256        |
| /19         | 255.255.224.0   | 32 C          | 8,128         |
| /20         | 255.255.240.0   | 16 C          | 4,064         |
| /21         | 255.255.248.0   | 8 C           | 2,032         |
| /22         | 255.255.252.0   | 4 C           | 1,016         |
| /23         | 255.255.254.0   | 2 C           | 508           |
| /24         | 255.255.255.0   | 1 C           | 254           |
| /25         | 255.255.255.128 | 2 subnets     | 124           |
| /26         | 255.255.255.192 | 4 subnets     | 62            |
| /27         | 255.255.255.224 | 8 subnets     | 30            |
| /28         | 255.255.255.240 | 16 subnets    | 14            |
| /29         | 255.255.255.248 | 32 subnets    | 6             |
| /30         | 255.255.255.252 | 64 subnets    | 2             |
| /31         | 255.255.255.254 | none          | none          |
| /32         | 255.255.255.255 | none          | 1             |

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