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Network Management and OperationsmediumMultiple ChoiceObjective-mapped

ANS-C01 Network Management and Operations Practice Question

Network Topology
$ aws ec2 describe-vpc-peering-connectionsvpc-peering-connection-ids pcx-12345678Refer to the exhibit.```"VpcPeeringConnections": ["Status": {"Code": "active","Message": "Active"},"AccepterVpcInfo": {"OwnerId": "111111111111","VpcId": "vpc-aaaaaaaa","CidrBlock": "10.0.0.0/16""RequesterVpcInfo": {"OwnerId": "222222222222","VpcId": "vpc-bbbbbbbb","CidrBlock": "192.168.0.0/16""Tags": []

Refer to the exhibit. A network engineer has established a VPC peering connection between VPC A (10.0.0.0/16) in account 111111111111 and VPC B (192.168.0.0/16) in account 222222222222. The peering connection status is 'active'. However, instances in VPC A cannot reach instances in VPC B. What is the MOST likely cause?

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

Route tables in one or both VPCs do not have routes to the peer CIDR

The VPC peering connection is active, so A is incorrect. The CIDR blocks (10.0.0.0/16 and 192.168.0.0/16) do not overlap, so D is incorrect. Security groups can block traffic, but the most common cause is missing routes in the route tables of one or both VPCs to the peer CIDR via the peering connection. Therefore, B is correct.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • The peering connection is not in the 'active' state

    Why it's wrong here

    Status shows 'active'.

  • Route tables in one or both VPCs do not have routes to the peer CIDR

    Why this is correct

    Missing routes prevent communication.

  • Security groups in VPC B are blocking traffic

    Why it's wrong here

    Possible but not the most likely.

  • The CIDR blocks overlap

    Why it's wrong here

    They are different.

Visual reference

192.168.1.0 /24 256 addresses (254 usable) 192.168.1.0 /25 Subnet A 128 addr (126 usable) 192.168.1.128 /25 Subnet B 128 addr (126 usable) Borrowing 1 bit from host portion creates 2 subnets (/25)

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Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

This ANS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the ANS-C01 exam.