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ANS-C01 Network Design Practice Question

Network Topology
$ aws ec2 describe-vpn-connectionsvpn-connection-ids vpn-12345678Refer to the exhibit.```"VpnConnections": ["VpnConnectionId": "vpn-12345678","State": "available","CustomerGatewayConfiguration": "...","Type": "ipsec.1","CustomerGatewayId": "cgw-12345678","VpnGatewayId": "vgw-12345678","Options": {"TunnelOptions": ["OutsideIpAddress": "203.0.113.1","TunnelInsideCidr": "169.254.10.0/30"},"OutsideIpAddress": "203.0.113.2","TunnelInsideCidr": "169.254.10.4/30""Routes": ["DestinationCidrBlock": "172.16.0.0/16","Source": "static","State": "available"

A network engineer is troubleshooting a VPN connection between an on-premises network (172.16.0.0/16) and an AWS VPC (10.0.0.0/16). The VPN status is 'available' but traffic is not passing. The engineer runs the command shown in the exhibit. What is the most likely cause of the issue?

⚠ Common exam trap

The trap here is that candidates see 'available' status and assume all components are working, but they overlook the critical requirement of a route in the VPC route table pointing to the virtual private gateway for the on-premises CIDR.

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

The VPC route table does not have a route for 172.16.0.0/16 pointing to the virtual private gateway.

The VPN status is 'available', which indicates that the VPN tunnels are established and the BGP sessions (if configured) are up. However, traffic still fails because the VPC route table lacks a route for the on-premises CIDR (172.16.0.0/16) pointing to the virtual private gateway (VGW). Without this route, the VPC does not know to send traffic destined for the on-premises network through the VPN connection, even though the tunnels themselves are operational.

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 VPN tunnels are not in 'UP' state.

    Why it's wrong here

    The state is 'available', meaning tunnels are up.

  • The VPC route table does not have a route for 172.16.0.0/16 pointing to the virtual private gateway.

    Why this is correct

    Without this route, VPC traffic to on-premises is dropped.

  • The tunnel inside CIDRs overlap with the VPC CIDR.

    Why it's wrong here

    169.254.x.x are link-local, not overlapping with 10.0.0.0/16.

  • The BGP session is not established.

    Why it's wrong here

    Static routes are used; BGP may not be configured.

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.