The correct answer is that the traffic originated from a web server (port 443) and was sent to a client (port 80). This is determined by interpreting VPC Flow Logs entries, where the source port field (443) indicates the HTTPS service on the server, and the destination port field (80) shows the HTTP client request, with protocol number 6 confirming TCP and the ACCEPT action verifying the traffic was allowed. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this tests your ability to read flow log fields in reverse—many candidates mistakenly assume the source IP is the client, but the source is always the originator of the packet, so a high source port like 443 means the server initiated the response. A common trap is confusing the direction of traffic when ports are reversed; remember that in a web server response, the server’s port (443) is the source, and the client’s ephemeral port (80) is the destination. Memory tip: “Source speaks first—443 from the server, 80 to the client.”
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
Exhibit
Refer to the exhibit. The following is a VPC Flow Logs entry:
2 123456789010 eni-1234567890abcdef 10.0.1.5 10.0.2.10 443 80 6 10 5000 1620000000 1620000060 ACCEPT OK
Based on the VPC Flow Logs entry, which of the following statements is correct?
Refer to the exhibit. The following is a VPC Flow Logs entry:
2 123456789010 eni-1234567890abcdef 10.0.1.5 10.0.2.10 443 80 6 10 5000 1620000000 1620000060 ACCEPT OK
A
The destination port is 443
Why wrong: Destination port is 80.
B
The protocol used is UDP
Why wrong: Protocol 6 is TCP.
C
The source IP address is 10.0.2.10
Why wrong: The source IP is 10.0.1.5.
D
The traffic originated from a web server (port 443) and was sent to a client (port 80)
Source port 443 indicates the server is sending data to a client on port 80.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The traffic originated from a web server (port 443) and was sent to a client (port 80)
Option B is correct because the source port is 443 (HTTPS) and destination port is 80 (HTTP). The protocol number 6 indicates TCP. The ACCEPT shows the traffic was allowed. Option A is wrong because the source is 10.0.1.5. Option C is wrong because the destination port is 80. Option D is wrong because the protocol is TCP (6).
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.
The traffic originated from a web server (port 443) and was sent to a client (port 80)
Why this is correct
Source port 443 indicates the server is sending data to a client on port 80.
Related concept
Static NAT maps one inside address to one outside address.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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.
Network Design — This question tests Network Design — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The traffic originated from a web server (port 443) and was sent to a client (port 80) — Option B is correct because the source port is 443 (HTTPS) and destination port is 80 (HTTP). The protocol number 6 indicates TCP. The ACCEPT shows the traffic was allowed. Option A is wrong because the source is 10.0.1.5. Option C is wrong because the destination port is 80. Option D is wrong because the protocol is TCP (6).
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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