ANS-C01 Network Implementation Practice Question
A company has a Direct Connect connection with a private VIF to a VPC. They want to use BGP to advertise a specific /24 prefix from their on-premises network to AWS. After configuration, the prefix is not visible in the VPC route tables. The BGP session is established. What should the company check?
⚠ Common exam trap
The ANS-C01 exam often tests the misconception that a BGP session being up guarantees routes are accepted, but the trap here is that AWS applies a mandatory prefix authorization list on Direct Connect virtual interfaces, and candidates overlook this filter when troubleshooting missing routes.
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
✓
Verify that the prefix is included in the allowed prefixes list for the Direct Connect virtual interface
When a BGP session is established but the advertised prefix does not appear in VPC route tables, the most likely cause is that the prefix is not included in the allowed prefixes list configured on the Direct Connect virtual interface. AWS uses this list as a prefix filter; any prefix received via BGP that is not in the allowed list is silently ignored and not installed in the VPC route tables.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Verify that the prefix is included in the allowed prefixes list for the Direct Connect virtual interface
Why this is correct
The virtual private gateway only accepts prefixes that are in the allowed prefix list.
- ✗
Ensure that route propagation is enabled on the VPC route table
Why it's wrong here
Route propagation is for VPN connections, not Direct Connect private VIF.
- ✗
Check that the BGP ASN on the customer gateway is unique and not conflicting
Why it's wrong here
The BGP session is established, so ASN is fine.
- ✗
Add a static route in the VPC route table for the on-premises prefix
Why it's wrong here
Static routes are not used with Direct Connect; the virtual private gateway automatically propagates routes that are in the allowed list.
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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.