| Class A | 1.0.0.0 – 126.255.255.255 · /8 default · 16M hosts/net |
| Class B | 128.0.0.0 – 191.255.255.255 · /16 default · 65,534 hosts/net |
| Class C | 192.0.0.0 – 223.255.255.255 · /24 default · 254 hosts/net |
| Class D | 224.0.0.0 – 239.255.255.255 · Multicast |
| Class E | 240.0.0.0 – 255.255.255.255 · Experimental/Reserved |
| Loopback | 127.0.0.0/8 · 127.0.0.1 for local stack testing |
| APIPA | 169.254.0.0/16 · Auto-assigned when DHCP fails |
| 10.0.0.0/8 | Class A private · 16,777,214 hosts |
| 172.16–31.x/12 | Class B private · 1,048,574 hosts |
| 192.168.x.x/16 | Class C private · 65,534 hosts |
| IPv6 fc00::/7 | Unique local (ULA) — equivalent of private |
| IPv6 fe80::/10 | Link-local (auto-assigned per interface) |
| IPv6 ::1/128 | Loopback (equivalent of 127.0.0.1) |
| Networks | 2ⁿ (n = bits borrowed from host portion) |
| Hosts/subnet | 2ʰ − 2 (h = remaining host bits) |
| Network ID | First address in block |
| Broadcast | Last address in block |
| First usable | Network ID + 1 |
| Last usable | Broadcast − 1 |
| Block size | 256 − subnet mask octet |
| 2000::/3 | Global Unicast (public routable) |
| fe80::/10 | Link-local (non-routable, auto-config) |
| fc00::/7 | Unique local (private, like RFC 1918) |
| ff00::/8 | Multicast |
| ::1/128 | Loopback |
| ::/128 | Unspecified |
| EUI-64 | Auto-generates host ID from MAC address |