Number of available IP addresses per private IP address range

0
votes

I have a problem with determining the correct number of available IP addresses per private IP address range for an AWS VPC for example.

Given that AWS allows assigning a range starting from a /16 block, I have the following available ranges. Given the fact they take 4 addresses away from me, this leaves me with the following ranges:

10.0.0.4 - 10.0.255.254
172.16.0.4 - 172.16.255.254
192.168.0.4 - 192.168.255.254

According to all calculators available on the internet, I get the same amount of IP addresses (65331). Nevertheless I've seen numerous recommendations to choose 10.0.0.0 as the address range, as it provides the highest number of IP addresses. Can somebody clarify this?

Thank you very much

1
amazon-web-servicesipcidr

1 Answers

1
votes

not sure if I understand your question too well, but I will try to shed some light on what you are asking. AWS uses those 4 IPS for their internal routing and configuration of their network.

Example VPC Address Range: 10.0.0.0/16

If you have this CIDR example, AWS takes the first 4 for their own resources of each SUBNET and you have access to the rest of these IPS in the given SUBNETS.

Now we can break that VPC down into smaller subnets so it can be used for different reasons such as the standard ( Pub / Private ).

Example Subnet : 10.0.0.0/27 = 32 IPS 32 - 4 = 28

AWS Also does not support .255(network broadcast address) of a subnet, so they take the last IP as well which gives you a total for 28 - 1 = 27 IPS for use.

Sources: https://docs.aws.amazon.com/vpc/latest/userguide/VPC_Subnets.html