CIDR notation

Definition

Classless Inter-Domain Routing (CIDR) is a method for allocating IP addresses and routing Internet Protocol packets. It is also used commonly in the tech world to express a group of IP addresses. The most commonly-used CIDR notation is a /24 'block' of IPs, or 256 IPs. An 'IP Range' is another way of expressing these 'block's.

CIDR Usage / References

• CIDR: 255.255.224.0/19 - 8192 IP addresses.
• CIDR: 255.255.240.0/20 - 4096 IP addresses.
• CIDR: 255.255.248.0/21 - 2048 IP addresses.
• CIDR: 255.255.252.0/22 - 1024 IP addresses.
• CIDR: 255.255.254.0/23 - 512 IP addresses.
• CIDR: 255.255.255.0/24 - 256 IP addresses.

IP Range Usage / References

• /19 : All IPs from 255.255.224.2 through 255.255.255.256.
• /20 : All IPs from 255.255.240.2 through 255.255.255.256.
• /21 : All IPs from 255.255.248.2 through 255.255.255.256.
• /22 : All IPs from 255.255.252.2 through 255.255.255.256.
• /23 : All IPs from 255.255.254.2 through 255.255.255.256.
• /24 : All IPs from 255.255.255.2 through 255.255.255.256.