Special-Use IPv4 Blocks (RFC 6890)
Complete reference of reserved IPv4 address blocks and their specific purposes.
Complete Special-Use IPv4 Ranges
| Network | Purpose | RFC | Routable | Description |
|---|---|---|---|---|
0.0.0.0/8 | This host on this network | RFC 1122 | No | Used for default routes and unspecified addresses |
10.0.0.0/8 | Private-Use Networks | RFC 1918 | No | Private addresses for internal networks (Class A) |
100.64.0.0/10 | Shared Address Space (CGNAT) | RFC 6598 | No | Carrier-Grade NAT, ISP shared addressing |
127.0.0.0/8 | Loopback | RFC 1122 | No | localhost addresses, typically 127.0.0.1 |
169.254.0.0/16 | Link Local (APIPA) | RFC 3927 | No | Auto-assigned when DHCP fails |
172.16.0.0/12 | Private-Use Networks | RFC 1918 | No | Private addresses for internal networks (Class B) |
192.0.0.0/24 | IETF Protocol Assignments | RFC 6890 | Yes | Special protocol use, some addresses globally routable |
192.0.2.0/24 | TEST-NET-1 | RFC 5737 | No | Documentation and example code |
192.88.99.0/24 | 6to4 Relay Anycast | RFC 3068 | Yes | IPv6 to IPv4 relay (deprecated) |
192.168.0.0/16 | Private-Use Networks | RFC 1918 | No | Private addresses for internal networks (Class C) |
198.18.0.0/15 | Network Interconnect Device Benchmark Testing | RFC 2544 | No | Performance testing between network devices |
198.51.100.0/24 | TEST-NET-2 | RFC 5737 | No | Documentation and example code |
203.0.113.0/24 | TEST-NET-3 | RFC 5737 | No | Documentation and example code |
224.0.0.0/4 | Multicast | RFC 1112 | Yes | IPv4 multicast addresses |
240.0.0.0/4 | Reserved for Future Use | RFC 1112 | No | Reserved block, not usable |
255.255.255.255/32 | Limited Broadcast | RFC 919 | No | Broadcast to all hosts on local network |
Common Address Categories
Private Networks (RFC 1918)
10.0.0.0/8
172.16.0.0/12
192.168.0.0/16
Never routed on the public internet
Test Networks (RFC 5737)
192.0.2.0/24
198.51.100.0/24
203.0.113.0/24
Safe for documentation and examples
Carrier-Grade NAT
100.64.0.0/10
ISP shared addressing space
Special Purpose
127.0.0.0/8
169.254.0.0/16
224.0.0.0/4
Loopback, link-local, multicast
Quick Recognition Tips
What Each Range Means
Private addresses (10.x, 172.16-31.x, 192.168.x) never appear on the public internet
100.64.x.x means your ISP is using Carrier-Grade NAT
169.254.x.x means DHCP failed and the device auto-configured
TEST-NET addresses are safe to use in documentation
224.x.x.x and above are multicast or reserved
Never use 240.x.x.x - it's reserved and may not work
Important Note
If you see 100.64.x.x addresses, your ISP is using Carrier-Grade NAT (CGNAT). This can cause issues with port
forwarding, gaming, and some applications that require direct connectivity.