IPv4 Subnet Cheat Sheet
Your quick-reference guide for all IPv4 network boundaries. Search by CIDR, Subnet Mask, or IP counts to instantly find the exact routing parameters you need.
| CIDR | Subnet Mask | Wildcard Mask | Total IPs | Usable Hosts | Typical Use / Notes |
|---|---|---|---|---|---|
| /0 | 0.0.0.0 | 255.255.255.255 | 4,294,967,296 | 4,294,967,294 | Default Route |
| /1 | 128.0.0.0 | 127.255.255.255 | 2,147,483,648 | 2,147,483,646 | Supernet / Block |
| /2 | 192.0.0.0 | 63.255.255.255 | 1,073,741,824 | 1,073,741,822 | Supernet / Block |
| /3 | 224.0.0.0 | 31.255.255.255 | 536,870,912 | 536,870,910 | Supernet / Block |
| /4 | 240.0.0.0 | 15.255.255.255 | 268,435,456 | 268,435,454 | Supernet / Block |
| /5 | 248.0.0.0 | 7.255.255.255 | 134,217,728 | 134,217,726 | Supernet / Block |
| /6 | 252.0.0.0 | 3.255.255.255 | 67,108,864 | 67,108,862 | Supernet / Block |
| /7 | 254.0.0.0 | 1.255.255.255 | 33,554,432 | 33,554,430 | Supernet / Block |
| /8 | 255.0.0.0 | 0.255.255.255 | 16,777,216 | 16,777,214 | Class A Network |
| /9 | 255.128.0.0 | 0.127.255.255 | 8,388,608 | 8,388,606 | Subnet |
| /10 | 255.192.0.0 | 0.63.255.255 | 4,194,304 | 4,194,302 | Subnet |
| /11 | 255.224.0.0 | 0.31.255.255 | 2,097,152 | 2,097,150 | Subnet |
| /12 | 255.240.0.0 | 0.15.255.255 | 1,048,576 | 1,048,574 | Subnet |
| /13 | 255.248.0.0 | 0.7.255.255 | 524,288 | 524,286 | Subnet |
| /14 | 255.252.0.0 | 0.3.255.255 | 262,144 | 262,142 | Subnet |
| /15 | 255.254.0.0 | 0.1.255.255 | 131,072 | 131,070 | Subnet |
| /16 | 255.255.0.0 | 0.0.255.255 | 65,536 | 65,534 | Class B Network |
| /17 | 255.255.128.0 | 0.0.127.255 | 32,768 | 32,766 | Subnet |
| /18 | 255.255.192.0 | 0.0.63.255 | 16,384 | 16,382 | Subnet |
| /19 | 255.255.224.0 | 0.0.31.255 | 8,192 | 8,190 | Subnet |
| /20 | 255.255.240.0 | 0.0.15.255 | 4,096 | 4,094 | Subnet |
| /21 | 255.255.248.0 | 0.0.7.255 | 2,048 | 2,046 | Subnet |
| /22 | 255.255.252.0 | 0.0.3.255 | 1,024 | 1,022 | Subnet |
| /23 | 255.255.254.0 | 0.0.1.255 | 512 | 510 | Subnet |
| /24 | 255.255.255.0 | 0.0.0.255 | 256 | 254 | Class C Network |
| /25 | 255.255.255.128 | 0.0.0.127 | 128 | 126 | Subnet |
| /26 | 255.255.255.192 | 0.0.0.63 | 64 | 62 | Subnet |
| /27 | 255.255.255.224 | 0.0.0.31 | 32 | 30 | Subnet |
| /28 | 255.255.255.240 | 0.0.0.15 | 16 | 14 | Subnet |
| /29 | 255.255.255.248 | 0.0.0.7 | 8 | 6 | Subnet |
| /30 | 255.255.255.252 | 0.0.0.3 | 4 | 2 | Point-to-Point (Legacy) |
| /31 | 255.255.255.254 | 0.0.0.1 | 2 | 2 | Point-to-Point (RFC 3021) |
| /32 | 255.255.255.255 | 0.0.0.0 | 1 | 1 | Single Host Route |
IPv4 Address Classes & Types
Historically, IP addresses were divided into "Classes" to manage the available address space before the introduction of CIDR. Below are the standard IPv4 classes and reserved private IP ranges used in modern networking.
Standard IPv4 Classes
| Class | First Octet Range | Default Subnet Mask | Primary Use Case |
|---|---|---|---|
| Class A | 1 - 126 | 255.0.0.0 (/8) | Massive corporate networks & ISPs |
| Class B | 128 - 191 | 255.255.0.0 (/16) | Medium to large organizations |
| Class C | 192 - 223 | 255.255.255.0 (/24) | Small business and home networks |
| Class D | 224 - 239 | N/A | Reserved strictly for Multicasting |
| Class E | 240 - 255 | N/A | Reserved for Experimental use |
Private IP Ranges (RFC 1918)
These addresses are not routable on the public internet and can be used freely by anyone on their internal local area networks (LAN).
| Network Class | IP Address Range | CIDR Block | Number of Available IPs |
|---|---|---|---|
| Class A Private | 10.0.0.0 – 10.255.255.255 | 10.0.0.0/8 | 16,777,216 |
| Class B Private | 172.16.0.0 – 172.31.255.255 | 172.16.0.0/12 | 1,048,576 |
| Class C Private | 192.168.0.0 – 192.168.255.255 | 192.168.0.0/16 | 65,536 |
Special Use IPv4 Addresses
| Address Range | Name / Designation | Purpose |
|---|---|---|
| 127.0.0.0/8 | Loopback (Localhost) | Used for testing local network interfaces (e.g., 127.0.0.1). |
| 169.254.0.0/16 | APIPA (Link-Local) | Auto-assigned when a device cannot reach a DHCP server. |
| 0.0.0.0/8 | Current Network | Often used as a default route designation in routing tables. |
| 255.255.255.255/32 | Global Broadcast | Used to broadcast messages to all hosts on the local network segment. |