| Address format |
Difference to last address |
Mask | Addresses | Relative to class A, B, C |
Restrictions | Typical use | |
|---|---|---|---|---|---|---|---|
| Decimal | 2n | ||||||
| a.b.c.d/32 | +0.0.0.0 | 255.255.255.255 | 1 | 20 | 1⁄256 C | Host route | |
| a.b.c.d/31 | +0.0.0.1 | 255.255.255.254 | 2 | 21 | 1⁄128 C | d = 0 … (2n) … 254 | Point to point links (RFC 3021) |
| a.b.c.d/30 | +0.0.0.3 | 255.255.255.252 | 4 | 22 | 1⁄64 C | d = 0 … (4n) … 252 | Point to point links (glue network) |
| a.b.c.d/29 | +0.0.0.7 | 255.255.255.248 | 8 | 23 | 1⁄32 C | d = 0 … (8n) … 248 | Smallest multi-host network |
| a.b.c.d/28 | +0.0.0.15 | 255.255.255.240 | 16 | 24 | 1⁄16 C | d = 0 … (16n) … 240 | Small LAN |
| a.b.c.d/27 | +0.0.0.31 | 255.255.255.224 | 32 | 25 | ⅛ C | d = 0 … (32n) … 224 | |
| a.b.c.d/26 | +0.0.0.63 | 255.255.255.192 | 64 | 26 | ¼ C | d = 0, 64, 128, 192 | |
| a.b.c.d/25 | +0.0.0.127 | 255.255.255.128 | 128 | 27 | ½ C | d = 0, 128 | Large LAN |
| a.b.c.0/24 | +0.0.0.255 | 255.255.255.0 | 256 | 28 | 1 C | ||
| a.b.c.0/23 | +0.0.1.255 | 255.255.254.0 | 512 | 29 | 2 C | c = 0 … (2n) … 254 | |
| a.b.c.0/22 | +0.0.3.255 | 255.255.252.0 | 1,024 | 210 | 4 C | c = 0 … (4n) … 252 | Small business |
| a.b.c.0/21 | +0.0.7.255 | 255.255.248.0 | 2,048 | 211 | 8 C | c = 0 … (8n) … 248 | Small ISP/ large business |
| a.b.c.0/20 | +0.0.15.255 | 255.255.240.0 | 4,096 | 212 | 16 C | c = 0 … (16n) … 240 | |
| a.b.c.0/19 | +0.0.31.255 | 255.255.224.0 | 8,192 | 213 | 32 C | c = 0 … (32n) … 224 | ISP/ large business |
| a.b.c.0/18 | +0.0.63.255 | 255.255.192.0 | 16,384 | 214 | 64 C | c = 0, 64, 128, 192 | |
| a.b.c.0/17 | +0.0.127.255 | 255.255.128.0 | 32,768 | 215 | 128 C | c = 0, 128 | |
| a.b.0.0/16 | +0.0.255.255 | 255.255.0.0 | 65,536 | 216 | 256 C = B | ||
| a.b.0.0/15 | +0.1.255.255 | 255.254.0.0 | 131,072 | 217 | 2 B | b = 0 … (2n) … 254 | |
| a.b.0.0/14 | +0.3.255.255 | 255.252.0.0 | 262,144 | 218 | 4 B | b = 0 … (4n) … 252 | |
| a.b.0.0/13 | +0.7.255.255 | 255.248.0.0 | 524,288 | 219 | 8 B | b = 0 … (8n) … 248 | |
| a.b.0.0/12 | +0.15.255.255 | 255.240.0.0 | 1,048,576 | 220 | 16 B | b = 0 … (16n) … 240 | |
| a.b.0.0/11 | +0.31.255.255 | 255.224.0.0 | 2,097,152 | 221 | 32 B | b = 0 … (32n) … 224 | |
| a.b.0.0/10 | +0.63.255.255 | 255.192.0.0 | 4,194,304 | 222 | 64 B | b = 0, 64, 128, 192 | |
| a.b.0.0/9 | +0.127.255.255 | 255.128.0.0 | 8,388,608 | 223 | 128 B | b = 0, 128 | |
| a.0.0.0/8 | +0.255.255.255 | 255.0.0.0 | 16,777,216 | 224 | 256 B = A | Largest IANA block allocation | |
| a.0.0.0/7 | +1.255.255.255 | 254.0.0.0 | 33,554,432 | 225 | 2 A | a = 0 … (2n) … 254 | |
| a.0.0.0/6 | +3.255.255.255 | 252.0.0.0 | 67,108,864 | 226 | 4 A | a = 0 … (4n) … 252 | |
| a.0.0.0/5 | +7.255.255.255 | 248.0.0.0 | 134,217,728 | 227 | 8 A | a = 0 … (8n) … 248 | |
| a.0.0.0/4 | +15.255.255.255 | 240.0.0.0 | 268,435,456 | 228 | 16 A | a = 0 … (16n) … 240 | |
| a.0.0.0/3 | +31.255.255.255 | 224.0.0.0 | 536,870,912 | 229 | 32 A | a = 0 … (32n) … 224 | |
| a.0.0.0/2 | +63.255.255.255 | 192.0.0.0 | 1,073,741,824 | 230 | 64 A | a = 0, 64, 128, 192 | |
| a.0.0.0/1 | +127.255.255.255 | 128.0.0.0 | 2,147,483,648 | 231 | 128 A | a = 0, 128 | |
| 0.0.0.0/0 | +255.255.255.255 | 0.0.0.0 | 4,294,967,296 | 232 | 256 A |
In common usage
