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Appendix D: CIDR Cheat Sheet
Classless Inter-Domain Routing (CIDR) is the latest refinement on how to present IP
Addresses and Subnet masks. CIDR replaces the previous generation of IP Address syntax,
Classful networks. Rather than allocating address blocks in 8-bit (octet) boundaries, it uses
a technique of a variable subnet mask to allow more allocation. With Optinet all IP Address
are presented as CIDR notations, i.e., the network address of 192.168.255.0 with a subnet
mask of 255.255.255.0 is presented as 192.168.255.0/24. Below is a CIDR Cheat Sheet
that will help you enter IP Address in CIDR notation.
CIDR Cheat Sheet
CIDR Notation
Class
Hosts
Mask
/32 1/256
C
1
255.255.255.255
/31 1/128
C
2
255.255.255.254
/30 1/64
C
4
255.255.255.252
/29 1/32
C
8
255.255.255.248
/28 1/16
C
16
255.255.255.240
/27 1/8
C
32
255.255.255.224
/26 1/4
C
64
255.255.255.192
/25 1/2
C
128
255.255.255.128
/24 1
C
256
255.255.255.0
/23 2
C
512
255.255.254.0