Subnet Mask Reference and Host Capacity Matrix
⏳ 2 min readComplete lookup table for CIDR prefixes from /16 to /32, listing subnet masks, wildcards, and host capacities.
CIDR to Subnet Mask Reference Table
Use this comprehensive lookup table to quickly reference common subnet divisions for IPv4 routing. This covers prefixes from `/16` down to `/32`.
| CIDR Prefix | Subnet Mask | Wildcard Mask | Total IPs | Usable Hosts | Typical Use Case |
|---|
| `/32` | `255.255.255.255` | `0.0.0.0` | 1 | 1 | Single Host Route / Loopback |
|---|
| `/31` | `255.255.255.254` | `0.0.0.1` | 2 | 2 | Point-to-Point Links (RFC 3021) |
|---|
| `/30` | `255.255.255.252` | `0.0.0.3` | 4 | 2 | Legacy Point-to-Point Router Links |
|---|
| `/29` | `255.255.255.248` | `0.0.0.7` | 8 | 6 | Small Office WAN / Edge Interfaces |
|---|
| `/28` | `255.255.255.240` | `0.0.0.15` | 16 | 14 | Small Department LAN |
|---|
| `/27` | `255.255.255.224` | `0.0.0.31` | 32 | 30 | Medium Department / Server Racks |
|---|
| `/26` | `255.255.255.192` | `0.0.0.63` | 64 | 62 | Large Floor / Guest Wi-Fi Segments |
|---|
| `/25` | `255.255.255.128` | `0.0.0.127` | 128 | 126 | Half of a standard Class C block |
|---|
| `/24` | `255.255.255.0` | `0.0.0.255` | 256 | 254 | Standard Home/Office Network |
|---|
| `/23` | `255.255.254.0` | `0.0.1.255` | 512 | 510 | Enterprise Branch Campus |
|---|
| `/22` | `255.255.252.0` | `0.0.3.255` | 1024 | 1022 | Large Enterprise LAN |
|---|
| `/16` | `255.255.0.0` | `0.0.255.255` | 65536 | 65534 | Massive Corporate Wide Area Network |
|---|
Understanding /31 Point-to-Point Links
Traditionally, a `/30` subnet was used to connect two routers together because it provided 4 IPs (1 network, 2 usable, 1 broadcast). However, RFC 3021 introduced the `/31` subnet specifically for point-to-point links.
In a `/31` subnet, the network and broadcast address rules are suspended. There are only two IPs, and both are completely usable, saving address space on large ISP backbones.
