CIDR Notation
Networking Topics > Layer 3 Routing > CIDR Notation
Classless Interdomain Routing (CIDR) is an industry standard notation for displaying subnet mask information in shorthand. CIDR notation uses just one number instead of a dotted-decimal subnet mask. The number represents the total number of subnet bits used in the subnet mask. The following table shows the possible CIDRs with their equivalent subnet masks.
| CIDR Prefix | Number of Hosts 2(32-CIDR) |
| /27 | 32 hosts |
| /26 | 64 hosts |
| /25 | 128 hosts |
| /24 | 256 hosts |
| /23 | 512 hosts |
| /22 | 1,024 hosts |
| /21 | 2,048 hosts |
| /20 | 4,096 hosts |
| /19 | 8,192 hosts |
| /18 | 16,384 hosts |
| /17 | 32,768 hosts |
| /16 | 65,536 hosts |
| /15 | 131,072 hosts |
| /14 | 262,144 hosts |
| /13 | 524,288 hosts |
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