CIDR¶
Resources¶
- Understanding CIDR Notation
- IPv4, CIDR, and VPC Subnets Made Simple!
- Visualize CIDRs
- Visual Subnet Calculator
Basics¶
CIDR: Classless Inter Domain Routing
An IPv4 IP address is made up of 32 bits:
If we want a representation of all IPs starting with 10.10, we can use the
CIDR representation as:
!!! note "number of hosts"
10.10.0.0/16 will give us a total of 256*256 hosts. Similarly,
10.10.0.0/24 will give us a total of 256 hosts.
!!! note "single IPv4 address"
A single IPv4 address in CIDR notation is: 10.10.101.5/32.
All Wildcards¶
If we want to represent the entire set of possible IPv4 addresses:
Example¶
Use this and this to visualize.
Let's say VPC CIDR is: 10.0.0.0/26, which means 64 total IPs (62 usable).
We can subnet this VPC into two subnets, having the following CIDRs:
10.0.0.0/2710.0.0.32/27
