RFC 1918 Private IP Ranges
The three private IPv4 address blocks and their common uses.
RFC 1918 reserves three blocks of IPv4 address space for private internets: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. Addresses in these private IP ranges are not routable on the public internet and can be reused freely inside any organization, which is why every home, office, and cloud network plans its space from them.
Choosing the right block depends on scale. The 10.0.0.0/8 range offers over 16 million addresses and is the standard choice for enterprise networks; 172.16.0.0/12 is the class B private range that mid-size networks and AWS VPCs default to; 192.168.0.0/16 is the familiar choice for SMB, branch, and home networks. Together the three ranges cover 17,891,328 addresses, and none of them will ever be assigned to a public destination.
| CIDR | Range Start | Range End | Hosts | Common Use |
|---|---|---|---|---|
| 10.0.0.0/8 | 10.0.0.0 | 10.255.255.255 | 16,777,216 | Large enterprise networks |
| 172.16.0.0/12 | 172.16.0.0 | 172.31.255.255 | 1,048,576 | Mid-size networks, AWS VPC default |
| 192.168.0.0/16 | 192.168.0.0 | 192.168.255.255 | 65,536 | SMB, home networks, branch offices |
Frequently Asked Questions
What are the private IP address ranges?
RFC 1918 defines three private IP ranges: 10.0.0.0/8 (10.0.0.0 to 10.255.255.255), 172.16.0.0/12 (172.16.0.0 to 172.31.255.255), and 192.168.0.0/16 (192.168.0.0 to 192.168.255.255). Every address inside those blocks is private, so you can reuse the same ranges on as many independent networks as you like.
What is the class B private IP range?
The class B private range is 172.16.0.0/12, which runs from 172.16.0.0 to 172.31.255.255 and contains 1,048,576 addresses. It was carved out of the old class B space, so people still call it the class B private range even though classful addressing has been replaced by CIDR.
How many private IP addresses are there?
17,891,328 in total: 16,777,216 in 10.0.0.0/8, 1,048,576 in 172.16.0.0/12, and 65,536 in 192.168.0.0/16. Because private addresses can be reused, the practical limit is how well you plan them rather than how many exist.
Are private IP addresses routable on the internet?
No. Internet routers drop traffic to and from RFC 1918 addresses, so private hosts reach public sites through NAT on a firewall or gateway, which rewrites the private source address to a public one.
Is 100.64.0.0/10 a private range?
No. 100.64.0.0/10 is the carrier-grade NAT range defined by RFC 6598. It behaves like private space and is not routable on the public internet, but it is a separate allocation from the three RFC 1918 ranges.
Which private IP range should I use?
Use 10.0.0.0/8 for large or multi-site enterprise networks, 172.16.0.0/12 for mid-size networks and cloud VPCs, and 192.168.0.0/16 for home, branch, and small business networks. Whichever you choose, plan the subnets in a single IPAM so blocks do not overlap when sites or clouds later connect.
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