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Subnet overview hands onΒΆ

We are navigating to subnets section and creating a new [[public subnet]] with 256 IP addresses ON Availability Zone A.

Then the same thing for Availability Zone B (change the Availability zone and CIDR block)

Then a [[Private Subnet]] A with 4096 IPs and a [[Private Subnet]] B.

When created, we notice that there are less available [[IP]]s than it should. This is because AWS reserves 5 [[IP]] addresses (first 4 and last 1 IP) in each Subnet. - These 5 IPs are not available for use and cannot be assigned to an instance - Ex, if CIDR block 10.0.0.0/24 reserved IP are: - 10.0.0.0 - [[network address]] - 10.0.0.1 - reserved by AWS for the [[VPC router]] - 10.0.0.2 - reserved by AWS for mapping to Amazon-provided DNS - 10.0.0.3 - reserved by AWS for future use - 10.0.0.255 - [[Network broadcast address]]. AWS does not support broadcast in a VPC, therefore the address is reserved.

  • Tip:
    • If you need 29 IP addresses for AWS EC2 instances, you can't choose a subnet of size /27 (32 IPs)
    • You need at least 64 [[IP]], [[Subnet size]] /26 (64-5=59 > 29, but 32-5=27<29)