AWS认证SAA-C03每日一题

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【SAA-C03助理级解决方案架构师认证】

A solutions architect is designing a VPC with public and private subnets.The VPC and subnets use IP 4 CIDR blocks.There is one public subnet and one private subnet in each of three Availability Zone(AZs) for high availability. An internet gateway is used to provide internet access for the public subnets.The private subnets require access to the internet to allow Amazon EC2 instances to download software updates. What should the solutions architect do to enable Intrnet access for the private subnets?
A  :   Create three NAT gateways, one for each public subnet in each AZ.
Create a private route table for each AZ that    forwards non-VPC traffic to the NAT gateway in its AZ.
B  :   Create three NAT gateways, one for each private subnet in each AZ.
Create a private route table for each AZ that forwards non-VPC traffic to the NAT gateway in its AZ.
C  :   Create second internet gateway on one of the private subnets.
Update the rout table for the private subnets that forward non-VPC traffic to the private internt gateway.

D  :   Create an egress-only internet gateway on one of the public subnets.
Update the route table for the private subnets that forward non-VPC traffic to the egress- only internet gateway.
正确答案      A

题目解析:
The correct answer is option A.  To enable Internet access for the private subnets,the solutions architect should create three NAT gateways, one for each public subnet in each Availability Zone(AZ). NAT gateways allow private instances to initiate outbound traffic to the Internet but do not allow inbound traffic from the Internet to reach the private instances.7
The solutions architect should then create a private route table for each AZ that forwards non-VPC traffic to the NAT gateway in its AZ.This will allow instances in the private subnets to access the Internet through the NAT gateways in the public subnets.