- A
Review the security group rules associated with the VPC resources to ensure they allow traffic from the on-premises network
Security groups act as a firewall for the instances.
- B
Confirm the customer gateway is associated with the correct VPC
Why wrong: Customer gateway is associated with the VPN connection, not the VPC directly.
- C
Verify that the VPC route tables include routes for the on-premises network pointing to the virtual private gateway
Without proper routes, traffic cannot be forwarded to the VPC.
- D
Verify that the on-premises network has a NAT device configured
Why wrong: NAT is not required for site-to-site VPN connectivity.
- E
Check that the VPN tunnel's status is 'UP'
Why wrong: The tunnel is already up.
Question 785 of 1,705
VPN Tunnel UP But No Traffic: Verify On-Premises Route to VPC
This ANS-C01 practice question tests your understanding of network management and operations. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network engineer is diagnosing a connectivity issue between an on-premises network and an Amazon VPC connected via a site-to-site VPN. The VPN tunnel is up, but traffic is not reaching the VPC. Which TWO actions should the engineer take to troubleshoot the issue? (Choose two.)
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
✓
Review the security group rules associated with the VPC resources to ensure they allow traffic from the on-premises network
Option A is correct because security groups act as a virtual firewall for VPC resources. If traffic from the on-premises network is not reaching the VPC, the security group rules must allow inbound traffic from the on-premises IP range. Option C is correct because the VPC route tables need a route for the on-premises network pointing to the virtual private gateway (VGW) to direct traffic correctly. Option B is incorrect because the customer gateway is the on-premises VPN endpoint, and its association with the VPC is already established since the VPN tunnel is up. Option D is incorrect because NAT is not a requirement for site-to-site VPN; the issue is about routing, not address translation. Option E is incorrect because the tunnel is already up, so checking its status again does not help diagnose why traffic is not flowing.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Review the security group rules associated with the VPC resources to ensure they allow traffic from the on-premises network
- ✗
Confirm the customer gateway is associated with the correct VPC
- ✓
Verify that the VPC route tables include routes for the on-premises network pointing to the virtual private gateway
Why this is correct
Without proper routes, traffic cannot be forwarded to the VPC.
Related concept
Static NAT maps one inside address to one outside address.
- ✗
Verify that the on-premises network has a NAT device configured
- ✗
Check that the VPN tunnel's status is 'UP'
Why it's wrong here
The tunnel is already up.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
Visual reference
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related ANS-C01 NAT questions on configuration and troubleshooting.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Management and Operations — This question tests Network Management and Operations — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Review the security group rules associated with the VPC resources to ensure they allow traffic from the on-premises network — Option A is correct because security groups act as a virtual firewall for VPC resources. If traffic from the on-premises network is not reaching the VPC, the security group rules must allow inbound traffic from the on-premises IP range. Option C is correct because the VPC route tables need a route for the on-premises network pointing to the virtual private gateway (VGW) to direct traffic correctly. Option B is incorrect because the customer gateway is the on-premises VPN endpoint, and its association with the VPC is already established since the VPN tunnel is up. Option D is incorrect because NAT is not a requirement for site-to-site VPN; the issue is about routing, not address translation. Option E is incorrect because the tunnel is already up, so checking its status again does not help diagnose why traffic is not flowing.
What should I do if I get this ANS-C01 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related ANS-C01 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Same concept, more angles
1 more ways this is tested on ANS-C01
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A network engineer is troubleshooting a Site-to-Site VPN connection between an on-premises network and AWS. The VPN tunnel is up, but traffic is not flowing from the on-premises network to a VPC. The VPC has a virtual private gateway attached, and the route table has a route pointing to the virtual private gateway for the on-premises CIDR (192.168.0.0/16). The on-premises firewall shows that traffic is being sent to the VPN tunnel. What should the engineer check next?
easy- A.Verify that the virtual private gateway is attached to the VPC.
- ✓ B.Verify that the on-premises route table has a route to the VPC CIDR via the VPN tunnel.
- C.Verify that the on-premises firewall is not blocking UDP port 500 for IKE.
- D.Verify that the VPN tunnel's pre-shared key matches on both sides.
Why B: Since the VPN tunnel is up and the on-premises firewall confirms traffic is being sent to the tunnel, the issue is likely on the on-premises routing side. For traffic to flow from on-premises to the VPC, the on-premises router must have a route pointing to the VPC CIDR via the VPN tunnel interface. Without this route, packets will not be forwarded into the tunnel, even though the tunnel itself is operational.
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Last reviewed: Jun 20, 2026
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