AWS Certified Solutions Architect – Professional SAP-C01 – Question347

A user has created a VPC with public and private subnets. The VPC has CIDR 20.0.0.0/16. The private subnet uses CIDR 20.0.1.0/24 and the public subnet uses CIDR 20.0.0.0/24. The user is planning to host a web server in the public subnet (port 80) and a DB server in the private subnet (port 3306). The user is configuring a security group of the NAT instance.
Which of the below mentioned entries is not required in NAT's security group for the database servers to connect to the Internet for software updates?

A. For Outbound allow Destination: 0.0.0.0/0 on port 443
B. For Inbound allow Source: 20.0.1.0/24 on port 80
C. For Inbound allow Source: 20.0.0.0/24 on port 80
D. For Outbound allow Destination: 0.0.0.0/0 on port 80

Correct Answer: C

Explanation:

Explanation: A user can create a subnet with VPC and launch instances inside that subnet. If the user has created a public private subnet to host the web server and DB server respectively, the user should configure that the instances in the private subnet can connect to the internet using the NAT instances. The user should first configure that NAT can receive traffic on ports 80 and 443 from the private subnet. Thus, allow ports 80 and 443 in Inbound for the private subnet 20.0.1.0/24. Now to route this traffic to the internet configure ports 80 and 443 in Outbound with destination 0.0.0.0/0. The NAT should not have an entry for the public subnet CIDR.
Reference:
http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_Scenario2…