Exam AWS-SysOps topic 1 question 824 discussion

Exam question from Amazon's AWS-SysOps

Question #: 824
Topic #: 1

A SysOps Administrator has implemented a VPC network design with the following requirements:
✑ Two Availability Zones (AZs)
✑ Two private subnets
✑ Two public subnets
✑ One internet gateway
✑ One NAT gateway
What would potentially cause applications in the VPC to fail during an AZ outage?

A. A single virtual private gateway, because it can be associated with a single AZ only.
B. A single internet gateway, because it is not redundant across both AZs.
C. A single NAT gateway, because it is not redundant across both AZs.
D. The default VPC route table, because it can be associated with a single AZ only.

Show Suggested Answer

Suggested Answer: D 🗳️

by kung07 at May 10, 2020, 9:02 a.m.

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kung07

Highly Voted 2 years, 9 months ago

C NAT gateway is created in a specific Availability Zone and implemented with redundancy in that zone only. To create an Availability Zone-independent architecture, create a NAT gateway in each Availability Zone and configure your routing to ensure that resources use the NAT gateway in the same Availability Zone. Refer to https://docs.aws.amazon.com/vpc/latest/userguide/vpc-nat-gateway.html

upvoted 23 times

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vob

Highly Voted 2 years, 8 months ago

Not A. Virtual Gateway is for VPN, irrelevant. Not B. IGW is a VPC resource, not an AZ resource. Not D. Default route table is for the entire VPC. C. Because NGW is placed in one of the two public subnets. The route table associated with the private subnets contains a route to 0.0.0.0/0 for the NGW. If the AZ with the NGW goes down, the remaining single private subnet in the other AZ can no longer communicate with the internet and could cause applications to fail.

upvoted 8 times

PeterGao

2 years, 8 months ago

thanks Vob, quite clear ans

upvoted 1 times

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albert_kuo

Most Recent 11 months, 2 weeks ago

Selected Answer: C

To ensure high availability and redundancy for outbound internet access in a multi-AZ VPC, it is recommended to deploy a NAT gateway in each AZ. This way, even if one AZ experiences an outage, the instances in the private subnets associated with the other AZ can still use the NAT gateway in their own AZ to maintain outbound internet connectivity.

upvoted 1 times

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gulu73

1 year, 5 months ago

Selected Answer: C

C is the answer

upvoted 1 times

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Cyril_the_Squirl

2 years, 8 months ago

C is Correct. Forget the scenario, just read all the statements in the answers and go back to the basics. Remember that each subnet must reside entirely within one Availability Zone and cannot span zones. You immediately see that C is correct.

upvoted 1 times

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