VPC Subnet Overlapping
Question
A user has created a VPC with CIDR 20.0.0.0/16
The user has created one subnet with CIDR 20.0.0.0/16 in this VPC.
The user is trying to create another subnet with the same VPC for CIDR 20.0.0.1/24
What will happen in this scenario?
Answers
Explanations
Click on the arrows to vote for the correct answer
A. B. C. D.Answer - A.
Since the CIDR overlaps for the first the second subnet, an overlap error will occur.
For more information on VPC subnets, please refer to the below link:
http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_Subnets.htmlIn AWS, a VPC (Virtual Private Cloud) is a virtual network that an AWS account can create within its own isolated section of the AWS cloud. The VPC's CIDR (Classless Inter-Domain Routing) block is the IP address range that the VPC uses.
A subnet is a range of IP addresses within the VPC's CIDR block. Each subnet must be associated with one route table and one availability zone.
In the scenario given, the user has created a VPC with the CIDR block 20.0.0.0/16 and a subnet with the same CIDR block as the VPC, 20.0.0.0/16. The user is now attempting to create another subnet within the same VPC, with the CIDR block 20.0.0.1/24.
Option A: It will throw a CIDR overlap error.
This option is incorrect. CIDR overlap error occurs when two or more CIDR blocks overlap, i.e., they share some IP addresses. However, in this scenario, the user is attempting to create a subnet with a smaller CIDR block than the VPC, so there is no overlap.
Option B: It is not possible to create a subnet with the same CIDR as the VPC.
This option is also incorrect. While it is not best practice to create a subnet with the same CIDR block as the VPC, it is technically possible. In this scenario, the user has already created one subnet with the same CIDR block as the VPC.
Option C: The second subnet will be created.
This option is correct. Since the CIDR block for the new subnet, 20.0.0.1/24, falls within the VPC's CIDR block, 20.0.0.0/16, the user can create the new subnet.
Option D: The VPC will modify the first subnet to allow this IP range.
This option is incorrect. The VPC does not modify existing subnets when a new subnet is created. Each subnet is assigned a specific CIDR block that cannot be changed after creation. If the user wants to add a new subnet that overlaps with an existing subnet, they need to use a different CIDR block for the new subnet.
In conclusion, the correct answer is C. The user can create the second subnet with CIDR 20.0.0.1/24 within the same VPC.
