About this interactive
RFC 1918 (1996) set aside three private IPv4 ranges, one from each of the old classes A, B and C:
- **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.
- **192.168.0.0/16**: 192.168.0.0 to 192.168.255.255.
Private addresses are not routed on the internet, so a router translates them to a public address on the way out: network address translation. Many private addresses can share a few public ones, which is how IPv4 has stretched this far.
The watch-outs are the edges: 172.15 and 172.32 are public, and so is 192.169.
What you'll learn
- Identify an IPv4 address as private (in an RFC 1918 range: 10.0.0.0/8, 172.16.0.0/12 or 192.168.0.0/16) or public
- Explain why private addresses need NAT to reach the internet: they are not routed on it
Aligned to
Cisco CCNA
1.7
Describe private IPv4 addressing
4.1
Configure and verify inside source NAT using static and pools
Key terms
- RFC 1918
- The internet standard that defines three private IPv4 address ranges reserved for use within private networks and not routable on the public internet.
- Private IPv4 Address
- An IP address from RFC 1918 ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) that is not routable on the public internet and must be translated before traversing it.
- Public IP Address
- A globally unique IP address assigned to a device or network that is routable and reachable across the public internet.
- Network Address Translation
NAT
- A method that maps private IP addresses to a public IP address, allowing multiple devices to share a single public IP.
Topics
Ip Addressing
Private Addresses
Rfc 1918
Nat
Interactive
Streak Sort
About TechKnowSurge
TechKnowSurge builds IT and cybersecurity professionals through hands-on, concept-first training built around real understanding — not memorization. Free interactive tools, structured programs, and 25+ years of real-world experience, all in one place.
Explore free tools and programs →