Understanding IPv4 Subnets
Choosing the right subnet size is crucial for cost efficiency and operational effectiveness. This guide explains CIDR notation and helps you select the optimal block size.
CIDR Notation Explained
CIDR (Classless Inter-Domain Routing) notation uses a slash followed by a number to indicate subnet size:
| CIDR | IP Count | Usable IPs | Typical Use |
|---|---|---|---|
| /24 | 256 | 254 | Small business, single service |
| /23 | 512 | 510 | Small-medium deployments |
| /22 | 1,024 | 1,022 | Medium infrastructure |
| /21 | 2,048 | 2,046 | Datacenter, hosting |
| /20 | 4,096 | 4,094 | Large hosting, ISP |
| /19 | 8,192 | 8,190 | Regional ISP |
| /18 | 16,384 | 16,382 | Large ISP |
| /17 | 32,768 | 32,766 | Major provider |
| /16 | 65,536 | 65,534 | Enterprise, large ISP |
Factors to Consider
- Current needs: How many IPs do you need right now?
- Growth projection: How fast will your needs grow?
- Budget: Larger blocks cost more total but less per IP
- Routability: /24 is generally the minimum routable block on the public internet
- Aggregation: Contiguous blocks can be aggregated for cleaner routing
Cost Efficiency
Per-IP prices typically decrease as block size increases. A /20 might cost $22 per IP while a /24 costs $35 per IP. If you need 1,000+ IPs, buying a larger block is almost always more economical.
Browse our marketplace to compare pricing across different subnet sizes.