Classes A–E with ranges, default masks, network/host counts, plus private and special ranges.
| Class | First octet | Default mask | Networks | Hosts/net | Use |
|---|---|---|---|---|---|
| A | 1–126 | 255.0.0.0 (/8) | 126 | 16,777,214 | Huge networks, legacy unicast |
| B | 128–191 | 255.255.0.0 (/16) | 16,384 | 65,534 | Medium networks, legacy unicast |
| C | 192–223 | 255.255.255.0 (/24) | 2,097,152 | 254 | Small LANs, legacy unicast |
| D | 224–239 | N/A (multicast) | — | — | Multicast groups, no host assignment |
| E | 240–255 | N/A (reserved) | — | — | Experimental, reserved |
Private (RFC1918): 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16
Special: 127.0.0.0/8 loopback · 169.254.0.0/16 APIPA · 224.0.0.0/4 multicast
Class is set by the first octet. A/B/C are unicast with default /8, /16, /24 masks. D is multicast, E is reserved. 127.x loopback and 0 are excluded from Class A.
Class C 192.168.1.0/24 → 254 usable hosts.RFC1918: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16. Not routable on the public internet.
169.254.0.0/16 self-assigned addresses when DHCP fails.