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🌐 Understanding IP Address Ranges
An IP address is a unique identifier assigned to each device connected to a network. Understanding how IP ranges are structured helps with network design, security, and troubleshooting.
🔢 IP Address Basics
- IPv4 addresses are written in dotted-decimal format:
192.168.1.1 - They consist of 4 octets (each 8 bits), totaling 32 bits
- Range:
0.0.0.0to255.255.255.255
📦 Public vs Private IP Ranges
| IP Range | Type | Use Case |
|---|---|---|
10.0.0.0/8 | Private | Internal networks (enterprise) |
172.16.0.0/12 | Private | Mid-size private networks |
192.168.0.0/16 | Private | Home and small office networks |
100.64.0.0/10 | Carrier-grade NAT | ISPs using NAT for customers |
127.0.0.1 | Loopback | Localhost testing |
169.254.0.0/16 | APIPA | Automatic IP when no DHCP |
📌 Private IPs are non-routable over the public internet—they’re meant for internal use behind NAT (e.g. routers, firewalls).
🔍 Public IPs
- Assigned by regional internet registries (ARIN, RIPE, APNIC)
- Routable over the internet
- Examples:
- Google DNS:
8.8.8.8 - Cloudflare DNS:
1.1.1.1 - BBC:
151.101.0.81
- Google DNS:
🧠 CIDR Notation (Classless Inter-Domain Routing)
| CIDR | Subnet Mask | Hosts Available | Example Network |
|---|---|---|---|
/8 | 255.0.0.0 | ~16 million | 10.0.0.0/8 |
/16 | 255.255.0.0 | ~65,000 | 192.168.0.0/16 |
/24 | 255.255.255.0 | 254 | 192.168.1.0/24 |
/30 | 255.255.255.252 | 2 (point-to-point) | 192.168.1.4/30 |
🚫 Reserved and Special-Purpose Ranges
| IP Range | Purpose |
|---|---|
127.0.0.0/8 | Loopback testing (localhost) |
169.254.0.0/16 | Link-local (no DHCP) |
224.0.0.0/4 | Multicast addresses |
240.0.0.0/4 | Reserved for future use |
255.255.255.255 | Broadcast address (local network) |
🛡️ Security & Firewall Tips
- 🔒 Block inbound access to private IP ranges from the internet
- 🔍 Monitor outbound traffic—private addresses in DNS or HTTP headers can indicate misconfig or malware
- 🌐 Use NAT to connect private IPs to the internet safely
- 🚫 Avoid exposing public services on IPs like
0.0.0.0unless necessary
✅ Summary
| Category | Example Range | Notes |
|---|---|---|
| Private | 192.168.1.0/24 | Internal only |
| Public | 8.8.8.8 | Routable, unique |
| Loopback | 127.0.0.1 | Localhost testing |
| APIPA | 169.254.x.x | No DHCP fallback |
| Multicast | 224.0.0.0/4 | Group-based messaging |
💡 Understanding IP ranges is the foundation of secure network design and defence.