Must be a valid lpv4 CIDR

Question

I'm working on the assignment and its asking me to create a VPC with a subnet open to the public.  No matter what I put into the IPv4 CIDR Block the IP address is invalid.

 

I tried  10.0.0.0/16  --- 28    always get the same error   “Must be a valid lpv4 CIDR".

Answer 1

So here in your issue, I would suggest a CIDR block 

10.20.0.0/16 as IPV4 CIDR 

you can then give 

10.20.1.0/24  this will help you to resolve this issue.

As per the documentation of aws, it clearly mentions that

The first four IP addresses and the last IP address in each subnet CIDR block are not available for you to use, and cannot be assigned to an instance. For example, in a subnet with CIDR block 10.0.0.0/24, the following five IP addresses are reserved:

10.0.0.0: Network address.

10.0.0.1: Reserved by AWS for the VPC router.

10.0.0.2: Reserved by AWS. The IP address of the DNS server is always the base of the VPC network range plus two; however, we also reserve the base of each subnet range plus two. For VPCs with multiple CIDR blocks, the IP address of the DNS server is located in the primary CIDR. For more information, see AWS Documentation.

10.0.0.3: Reserved by AWS for future use.

10.0.0.255: Network broadcast address. We do not support broadcast in a VPC, therefore we reserve this address.