RFC 1918 Private Range: 10.0.0.0/8
Convert the RFC 1918 10.0.0.0 private network range to CIDR. Understand the largest private IP block with 16 million addresses and its common uses.
Detailed Explanation
RFC 1918: The 10.0.0.0/8 Private Network
RFC 1918 defines three private IPv4 address ranges that are not routable on the public internet. The 10.0.0.0/8 block is the largest, containing 16,777,216 addresses.
The Three RFC 1918 Ranges
| Range | CIDR | Addresses |
|---|---|---|
| 10.0.0.0 - 10.255.255.255 | 10.0.0.0/8 | 16,777,216 |
| 172.16.0.0 - 172.31.255.255 | 172.16.0.0/12 | 1,048,576 |
| 192.168.0.0 - 192.168.255.255 | 192.168.0.0/16 | 65,536 |
10.0.0.0/8 Breakdown
Range: 10.0.0.0 - 10.255.255.255
CIDR: 10.0.0.0/8
Mask: 255.0.0.0
Addresses: 16,777,216
Common Subdivision Patterns
Organizations typically subdivide the /8 space:
| Pattern | Purpose |
|---|---|
| 10.{region}.0.0/16 | Per-region allocation |
| 10.{dept}.{floor}.0/24 | Per-department subnets |
| 10.{vpc-id}.0.0/16 | Per-VPC in cloud |
| 10.{env}.0.0/16 | Per-environment (dev/staging/prod) |
Cloud VPC Usage
The 10.0.0.0/8 range is the most popular choice for cloud VPCs:
- AWS default VPC: 172.31.0.0/16 (but custom VPCs often use 10.x)
- GCP: Commonly uses 10.128.0.0/9 for auto-mode VPCs
- Azure: Often starts with 10.0.0.0/16 for new VNets
Non-Aligned Subranges
Sometimes you need to convert a sub-range that doesn't align to a clean CIDR:
Range: 10.0.0.0 - 10.0.5.255
Result: 10.0.0.0/22, 10.0.4.0/23
This range of 1,536 addresses requires two CIDR blocks because 1,536 is not a power of 2.
Use Case
A network architect is planning the IP address scheme for a new corporate network that spans three data centers. They need to carve the 10.0.0.0/8 space into per-site allocations and convert each site's range to CIDR for router and firewall configuration.