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Question 996 of 1,705

Network Design →easyMultiple ChoiceObjective-mapped

Quick Answer

The answer is to use the same BGP ASN for both Direct Connect and VPN, and set a higher MED on the VPN routes. This configuration ensures symmetric routing by making AWS treat both connections as a single BGP session, allowing you to control active/passive failover through the Multi-Exit Discriminator attribute, where the higher MED on the VPN path makes it the backup. On the ANS-C01 exam, this question tests your understanding of BGP path selection and hybrid network design, specifically how to maintain traffic symmetry when combining a private VIF with a VPN backup—a common trap is assuming different ASNs are needed for separate connections, which would cause asymmetric routing. Remember the key memory tip: same ASN, higher MED on the backup; this keeps traffic flowing symmetrically and ensures failover works predictably.

ANS-C01 Network Design Practice Question

This ANS-C01 practice question tests your understanding of network design. 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 company is deploying a hybrid network with AWS Direct Connect and a VPN backup. The Direct Connect virtual interface is configured for private VIF with BGP. The VPN uses IPsec tunnels over the internet. What is the best practice to ensure symmetric routing and failover?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.

Question 1easymultiple choice

Open the full BGP breakdown →

A
Configure ASN prepending on the VPN BGP advertisements to make them less preferred.
Why wrong: ASN prepending is one method, but not the best practice for symmetric routing; it's used to influence path selection.
B
Use different BGP ASNs for Direct Connect and VPN to allow AWS to prefer the Direct Connect path.
Why wrong: Different ASNs can cause asymmetric routing and are not recommended for failover.
C
Disable BGP on the Direct Connect private VIF and use static routes to force traffic through Direct Connect.
Why wrong: Private VIF requires BGP; static routes are not supported on private VIF.
D
Use the same BGP ASN for both Direct Connect and VPN, and set a higher MED (Multi-Exit Discriminator) on the VPN routes.
Same ASN ensures AWS sees both as same neighbor, and MED controls preference.

Full breakdown with real-world context →

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

✓

Use the same BGP ASN for both Direct Connect and VPN, and set a higher MED (Multi-Exit Discriminator) on the VPN routes.

Option B is correct. Using the same BGP ASN on the VPN side ensures that AWS treats both paths as equal, and with BGP attributes you can control active/passive behavior. Option A is wrong because ASN prepending is used to influence path selection, not to ensure symmetry. Option C is wrong because you cannot disable BGP on Direct Connect private VIF; it requires BGP. Option D is wrong because using different ASNs would make AWS treat them as separate paths and might cause asymmetric routing.

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.

✗
Configure ASN prepending on the VPN BGP advertisements to make them less preferred.
Why it's wrong here
ASN prepending is one method, but not the best practice for symmetric routing; it's used to influence path selection.
✗
Use different BGP ASNs for Direct Connect and VPN to allow AWS to prefer the Direct Connect path.
Why it's wrong here
Different ASNs can cause asymmetric routing and are not recommended for failover.
✗
Disable BGP on the Direct Connect private VIF and use static routes to force traffic through Direct Connect.
Why it's wrong here
Private VIF requires BGP; static routes are not supported on private VIF.
✓
Use the same BGP ASN for both Direct Connect and VPN, and set a higher MED (Multi-Exit Discriminator) on the VPN routes.
Why this is correct
Same ASN ensures AWS sees both as same neighbor, and MED controls preference.
Clue confirmation
The clue word "best" in the question point toward this answer.
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.

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FAQ

Questions learners often ask

What does this ANS-C01 question test?

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: Use the same BGP ASN for both Direct Connect and VPN, and set a higher MED (Multi-Exit Discriminator) on the VPN routes. — Option B is correct. Using the same BGP ASN on the VPN side ensures that AWS treats both paths as equal, and with BGP attributes you can control active/passive behavior. Option A is wrong because ASN prepending is used to influence path selection, not to ensure symmetry. Option C is wrong because you cannot disable BGP on Direct Connect private VIF; it requires BGP. Option D is wrong because using different ASNs would make AWS treat them as separate paths and might cause asymmetric routing.

What should I do if I get this ANS-C01 question wrong?

Are there clue words in this question I should notice?

Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.

What is the key concept behind this question?

Static NAT maps one inside address to one outside address.

About these practice questions

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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 company is designing a hybrid network using AWS Direct Connect and VPN backup. The company wants to ensure that traffic always uses Direct Connect when it is available. Which TWO configurations should be implemented? (Choose TWO.)

medium

✓ A.Use AS_PATH prepending on the VPN BGP session to make the VPN path less preferred.
✓ B.Advertise more specific prefixes over Direct Connect and less specific prefixes over VPN.
C.Disable BGP on the VPN connection to force traffic to Direct Connect.
D.Set a lower MED value on the Direct Connect BGP session.
E.Advertise the same prefixes over both connections with the same AS_PATH length.

Why A: AS_PATH prepending on the VPN BGP session increases the AS_PATH length for routes advertised over the VPN, making them less preferred compared to the same routes learned over Direct Connect with a shorter AS_PATH. BGP selects the path with the shortest AS_PATH length, so traffic will use Direct Connect when it is available. This is a standard technique for influencing outbound traffic path selection in a hybrid network.

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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.