Private IP Ranges Reference
Every reserved IPv4 block: RFC 1918, CGNAT, loopback, link-local, multicast. With which-to-pick guidance.
The reserved IPv4 blocks, complete
These are all the IPv4 ranges that aren't publicly routable on the internet. Memorizing the top three (RFC 1918) covers 95% of real-world use, but the other rows occasionally bite you.
| Range | CIDR | RFC | Use |
|---|---|---|---|
| 10.0.0.0 – 10.255.255.255 | 10.0.0.0/8 | RFC 1918 | Private — large networks |
| 172.16.0.0 – 172.31.255.255 | 172.16.0.0/12 | RFC 1918 | Private — mid-size networks |
| 192.168.0.0 – 192.168.255.255 | 192.168.0.0/16 | RFC 1918 | Private — home and small office |
| 100.64.0.0 – 100.127.255.255 | 100.64.0.0/10 | RFC 6598 | CGNAT (carrier-grade NAT) |
| 127.0.0.0 – 127.255.255.255 | 127.0.0.0/8 | RFC 1122 | Loopback (localhost) |
| 169.254.0.0 – 169.254.255.255 | 169.254.0.0/16 | RFC 3927 | Link-local (APIPA — DHCP failure) |
| 0.0.0.0 – 0.255.255.255 | 0.0.0.0/8 | RFC 1122 | "This network" — unspecified source |
| 224.0.0.0 – 239.255.255.255 | 224.0.0.0/4 | RFC 5771 | Multicast |
| 240.0.0.0 – 255.255.255.254 | 240.0.0.0/4 | RFC 1112 | Reserved (Class E) |
| 255.255.255.255 | 255.255.255.255/32 | RFC 919 | Limited broadcast |
| 192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24 | — | RFC 5737 | TEST-NET (use in documentation) |
| 198.18.0.0 – 198.19.255.255 | 198.18.0.0/15 | RFC 2544 | Benchmark testing |
RFC 1918 — the three you'll actually use
For private networks behind NAT, pick from these three. The choice usually comes down to:
- 192.168.0.0/16 — what consumer routers default to. Easy to memorize. Use it for home and small office unless you have a reason not to.
- 10.0.0.0/8 — vastly bigger, useful when you need many subnets (e.g., enterprise VLANs, multiple sites with site-to-site VPN, container networks). Common to see
10.<site>.<vlan>.0/24. - 172.16.0.0/12 — least common, makes a good "neutral" choice for VPN-connected networks since it's less likely to overlap with someone else's home or office network.
If you ever VPN into your home network from a coffee shop, hotel, or relative's house, your home subnet will conflict with theirs if both use 192.168.1.0/24. This is the #1 cause of "VPN connects but I can't reach anything" issues. Pick something less common at home (10.42.0.0/24, 172.20.0.0/24, etc.) to dodge the conflict.
CGNAT (100.64.0.0/10) — why your router shows a "weird" IP
If your home router's WAN side shows an address starting with 100.64–100.127, your ISP is using CGNAT. They're sharing one public IP across many customers. Implications:
- Port forwarding from the internet won't work (no public IP to forward from).
- Some games and VoIP have NAT traversal issues.
- The fix is asking your ISP for a real public IP — usually free if you ask, sometimes a small extra fee.