In private IP address, used to divide IP address with Classes
Class Method
| Class |
Reserved IP address range | Subnet Mask |
| class A | 10.0.0.0 - 10.255.255.255 | 255.0.0.0 |
| class B | 172.16.0.0 - 172.31.255.255 | 255.240.0.0 |
| class C | 192.168.0.0 - 192.168.255.255 | 255.255.0.0 |
Classless Method
→ CIDR
CIDR is an IP address allocation method that improves data routing efficiency on the internet.
- CIDR Block: range of IP addresses
- CIDR Notation: range of CIDR Block
[AWS Subnet]
In AWS subnet, the allowed CIDR block sizes for a subnet range from /16 to /28.
- /16: Allows for 65,536 IP addresses (65,534 usable).
- /28: Allows for 16 IP addresses (14 usable).
This means that the smallest subnet you can create has a /28 prefix (which provides 16 IP addresses, 14 of which are usable), and the largest subnet you can create has a /16 prefix (which provides 65,536 IP addresses, 65,534 of which are usable).
https://docs.aws.amazon.com/vpc/latest/userguide/subnet-sizing.html#subnet-sizing-ipv4
Subnet CIDR blocks - Amazon Virtual Private Cloud
Subnet CIDR blocks The IP addresses for your subnets are represented using Classless Inter-Domain Routing (CIDR) notation. The CIDR block of a subnet can be the same as the CIDR block for the VPC (to create a single subnet in the VPC), or a subset of the C
docs.aws.amazon.com
