The correct answer involves using different ASNs, different BGP community tags, and different prefix lengths for each Direct Connect connection. This combination ensures high availability by preventing BGP loop prevention from discarding routes when the same on-premises prefixes are advertised from two separate paths, while the different community tags allow you to influence routing policies with your provider, and the varying prefix lengths enable AWS to prefer the more specific route for optimal traffic flow. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this question tests your understanding of how BGP attributes interact with Direct Connect to achieve both redundancy and path selection, often trapping candidates who assume identical MED values or identical prefixes are sufficient. A common mistake is thinking you must use the same ASN for both connections, but that would cause AWS to discard the second advertisement as a loop. Remember the mnemonic “ASN, Community, Prefix” to recall the three pillars of Direct Connect BGP high availability.
ANS-C01 Network Management and Operations Practice Question
This ANS-C01 practice question tests your understanding of network management and operations. 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.
A company is designing a highly available hybrid network using two AWS Direct Connect connections from different providers. The company wants to use BGP to advertise the same on-premises prefixes to AWS. Which THREE practices should be followed to ensure high availability and optimal traffic flow? (Choose three.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Advertise the same prefixes with different prefix lengths to influence route selection
Option A is correct because using different ASNs prevents BGP loop prevention from discarding routes. Option B is correct because using different BGP communities can influence routing policies. Option D is correct because using different prefix lengths allows AWS to prefer the more specific prefix. Option C is wrong because using the same MED value would not help in path selection. Option E is wrong because advertising the same prefixes on both connections is necessary for redundancy.
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.
✗
Advertise different on-premises prefixes on each connection
Why it's wrong here
All prefixes should be advertised on both connections for full redundancy.
✓
Advertise the same prefixes with different prefix lengths to influence route selection
Why this is correct
AWS prefers more specific prefixes (longer prefix length).
Related concept
Static NAT maps one inside address to one outside address.
✓
Configure a unique private ASN for each Direct Connect connection
Why this is correct
Different ASNs prevent BGP loop prevention from rejecting routes.
Related concept
Static NAT maps one inside address to one outside address.
✗
Set the same MED value for prefixes advertised on both connections
Why it's wrong here
Using the same MED does not help differentiate paths.
✓
Use different BGP community tags for each connection to influence routing policies
Why this is correct
BGP communities can be used to set local preference on AWS.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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 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: Advertise the same prefixes with different prefix lengths to influence route selection — Option A is correct because using different ASNs prevents BGP loop prevention from discarding routes. Option B is correct because using different BGP communities can influence routing policies. Option D is correct because using different prefix lengths allows AWS to prefer the more specific prefix. Option C is wrong because using the same MED value would not help in path selection. Option E is wrong because advertising the same prefixes on both connections is necessary for redundancy.
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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Question Discussion
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