Network Classless Inter Domain Routing (CIDR) Cheat Sheet – POFTUT

Network Classless Inter Domain Routing (CIDR) Cheat Sheet

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Internet and most of the network infrastructures uses IP Protocol. IP protocol uses IP addresses in order to connect different hosts and networks over globe. Classless Inter Domain Routing or CIDR is hierarchical IP addressing scheme used to set IP addresses to the hosts and network. Here we will learn how to calculate IP address, Network Address, Broadcast Address, Network Mask and provide these as cheat sheet.

IP address, Network Address, Broadcast Address, Network Mask Calculation

We will calculate given network parameters in this part we can use following cheat sheet. In this example we will use 192.168.1.0 as network address. We need 10 IP address for our host. If we look to the table we see that Potential host numbers a 2 and its multiply. So we will use 16 host line which have /28 network mask or 255.255.255.240 . So the network information will be like below.

Network Address: 192.168.1.0

Host IP Range: 192.168.1.1 - 192.168.1.10

Actual Useable Host IP Count:  14

Broadcast Address: 192.168.1.15

CIDR Cheat Sheet

Here is some explanation

  • Prefix is bit count for network address
  • Amount Of a Class C is how many C class network can be created in this network
  • Potential Hosts is the count of IP numbers
  • Actual Hosts is the count of usable IP numbers because 1 IP is used for network address and 1 IP is used for broadcast purposes.
  • Netmask is decimal presentation of the prefix with IP format.
Prefix Amount Of a Class C Potential Hosts Actual Hosts Netmask # of subnets
/31 1/128 2 0 255.255.255.254 128
/30 1/64 4 2 255.255.255.252 64
/29 1/32 8 6 255.255.255.248 32
/28 1/16 16 14 255.255.255.240 16
/27 1/8 32 30 255.255.255.224 8
/26 1/4 64 62 255.255.255.192 4
/25 1/2 128 126 255.255.255.128 2
/24 1 256 254 255.255.255.0 1
/23 2 512 510 255.255.254.0 128
/22 4 1,024 1,022 255.255.252.0 64
/21 8 2,048 2,046 255.255.248.0 32
/20 16 4,096 4,094 255.255.240.0 16
/19 32 8,192 8,190 255.255.224.0 8
/18 64 16,384 16,382 255.255.192.0 4
/17 128 32,768 32,766 255.255.128.0 2
/16 256 = 1 class B net 65,536 65,534 255.255.0.0 1
/15 512 = 2 B nets 131,072 131,070 255.254.0.0 128
/14 1,024 = 4 B nets 262,144 262,142 255.252.0.0 64
/13 2,048 = 8 B nets 524,288 524,286 255.248.0.0 32
/12 4,096 = 16 B nets 1,048,576 1,048,574 255.240.0.0 16
/11 8,192 = 32 B nets 2,097,152 2,097,150 255.224.0.0 8
/10 16,384 = 64 B nets 4,194,304 4,194,302 255.192.0.0 4
/9 32,768 = 128 B nets 8,388,608 8,388,606 255.128.0.0 2
/8 65,536 = 256 B nets = 1 A net 16,777,216 16,777,214 255.0.0.0 1
/7 131,072 = 2 A nets 33,554,432 33,554,430 254.0.0.0 128
/6 262,144 = 4 A nets 67,108,864 67,108,862 252.0.0.0 64
/5 524,888 = 8 A nets 134,217,728 134,217,726 248.0.0.0 32
/4 1,048,576 = 16 A nets 268,435,456 268,435,454 240.0.0.0 16
/3 2,097,152 = 32 A nets 536,870,912 536,870,910 224.0.0.0 8
/2 4,194,304 = 64 A nets 1,073,741,824 1,073,741,822 192.0.0.0 4
/1 8,388,608 = 128 A nets 2,147,483,648 2,147,483,646 128.0.0.0 2
/0 16,777,216 = 256 A nets 4,294,967,296 4,294,967,294 0.0.0.0 1
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Another CIDR Cheat Sheet

CIDR        Total number    Network             Description:
Notation:   of addresses:   Mask:
--------------------------------------------------------------
/0          4,294,967,296   0.0.0.0             Every Address
/1          2,147,483,648   128.0.0.0           128 /8 nets
/2          1,073,741,824   192.0.0.0           64 /8 nets
/3          536,870,912     224.0.0.0           32 /8 nets
/4          268,435,456     240.0.0.0           16 /8 nets
/5          134,217,728     248.0.0.0           8 /8 nets
/6          67,108,864      252.0.0.0           4 /8 nets
/7          33,554,432      254.0.0.0           2 /8 nets
/8          16,777,214      255.0.0.0           1 /8 net (Class A)
--------------------------------------------------------------
/9          8,388,608       255.128.0.0         128 /16 nets
/10         4,194,304       255.192.0.0         64 /16 nets
/11         2,097,152       255.224.0.0         32 /16 nets
/12         1,048,576       255.240.0.0         16 /16 nets
/13         524,288         255.248.0.0         8 /16 nets
/14         262,144         255.252.0.0         4 /16 nets
/15         131.072         255.254.0.0         2 /16 nets
/16         65,536          255.255.0.0         1 /16 (Class B)
--------------------------------------------------------------
/17         32,768          255.255.128.0       128 /24 nets
/19         16,384          255.255.192.0       64 /24 nets
/19         8,192           255.255.224.0       32 /24 nets
/20         4,096           255.255.240.0       16 /24 nets
/21         2,048           255.255.248.0       8 /24 nets
/22         1,024           255.255.252.0       4 /24 nets
/23         512             255.255.254.0       2 /24 nets
/24         256             255.255.255.0       1 /24 (Class C)
--------------------------------------------------------------
/25         128             255.255.255.128     Half of a /24
/26         64              255.255.255.192     Fourth of a /24
/27         32              255.255.255.224     Eighth of a /24
/28         16              255.255.255.240     1/16th of a /24
/29         8               255.255.255.248     5 Usable addresses
/30         4               255.255.255.252     1 Usable address
/31         2               255.255.255.254     Unusable
/32         1               255.255.255.255     Single host
--------------------------------------------------------------
Reserved Space:
    0.0.0.0/8   
    127.0.0.0/8
    192.0.2.0/24
    10.0.0.0/8
    172.16.0.0/12
    192.168.0.0/16
    169.254.0.0/16

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