
CIDR Table
Content Leader: Jess Garcia - Last Updated: December 24, 2006
CIDR Table
RFC 1123
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/n -> n=number of bits in mask
| Prefix | Netmask | Binary | Number of Networks | Hosts | |
| /1 | 128.0.0.0 | 10000000000000000000000000000000 | 128 Class A domains | 2,147,483,392 | |
| /2 | 192.0.0.0 | 11000000000000000000000000000000 | 64 Class A domains | 1,073,741,696 | |
| /3 | 224.0.0.0 | 11100000000000000000000000000000 | 32 Class A domains | 536,870,848 | |
| /4 | 240.0.0.0 | 11110000000000000000000000000000 | 16 Class A domains | 268,435,424 | |
| /5 | 248.0.0.0 | 11111000000000000000000000000000 | 8 Class A domains | 134,217,712 | |
| /6 | 252.0.0.0 | 11111100000000000000000000000000 | 4 Class A domains | 67,108,856 | |
| /7 | 254.0.0.0 | 11111110000000000000000000000000 | 2 Class A domains | 33,554,428 | |
| /8 | 255.0.0.0 | 11111111000000000000000000000000 | 1 Class A domain | 16,777,214 | |
| /9 | 255.128.0.0 | 11111111100000000000000000000000 | 128 Class B domains | 8,388,352 | |
| /10 | 255.192.0.0 | 11111111110000000000000000000000 | 64 Class B domains | 4,194,176 | |
| /11 | 255.224.0.0 | 11111111111000000000000000000000 | 32 Class B domains | 2,097,088 | |
| /12 | 255.240.0.0 | 11111111111100000000000000000000 | 16 Class B domains | 1,048,544 | |
| /13 | 255.248.0.0 | 11111111111110000000000000000000 | 8 Class B domains | 524,272 | |
| /14 | 255.252.0.0 | 11111111111111000000000000000000 | 4 Class B domains | 262,136 | |
| /15 | 255.254.0.0 | 11111111111111100000000000000000 | 2 Class B domains | 131,068 | |
| /16 | 255.255.0.0 | 11111111111111110000000000000000 | 1 Class B domain | 65,024 | |
| /17 | 255.255.128.0 | 11111111111111111000000000000000 | 128 Class C domains | 32,512 | |
| /18 | 255.255.192.0 | 11111111111111111100000000000000 | 64 Class C domains | 16,256 | |
| /19 | 255.255.224.0 | 11111111111111111110000000000000 | 32 Class C domains | 8,128 | |
| /20 | 255.255.240.0 | 11111111111111111111000000000000 | 16 Class C domains | 4,064 | |
| /21 | 255.255.248.0 | 11111111111111111111100000000000 | 8 Class C domains | 2,032 | |
| /22 | 255.255.252.0 | 11111111111111111111110000000000 | 4 Class C domains | 1,016 | |
| /23 | 255.255.254.0 | 11111111111111111111111000000000 | 2 Class C domains | 508 | |
| /24 | 255.255.255.0 | 11111111111111111111111100000000 | 1 Class C domain | 254 | |
| /25 | 255.255.255.128 | 11111111111111111111111110000000 | 2 subnets | 124 | |
| /26 | 255.255.255.192 | 11111111111111111111111111000000 | 4 subnets | 62 | |
| /27 | 255.255.255.224 | 11111111111111111111111111100000 | 8 subnets | 30 | |
| /28 | 255.255.255.240 | 11111111111111111111111111110000 | 16 subnets | 14 | |
| /29 | 255.255.255.248 | 11111111111111111111111111111000 | 32 subnets | 6 | |
| /30 | 255.255.255.252 | 11111111111111111111111111111100 | 64 subnets | 2 | |
| /31 | 255.255.255.254 | 11111111111111111111111111111110 | none | none | |
| /32 | 255.255.255.255 | 11111111111111111111111111111111 | 1/256 Class C | 1 | |
Reserved Networks
| Class | Start | End | Hosts | Networks | |
| A | 10.0.0.0 | 10.255.255.255 | 16,777,216 | 1 A network | |
| B | 172.16.0.0 | 172.31.255.255 | 1,048,544 | 16 B networks | |
| C | 192.168.0.0 | 192.168.255.255 | 65,534 | 256 C networks | |
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