ANS-C01 Network Management and Operations Practice Question
A company has a VPC with a CIDR of 10.0.0.0/16 and needs to connect to a partner VPC with CIDR 10.0.0.0/16. Both VPCs are in the same region. They want to use VPC Peering. After creating the peering connection and adding routes, connectivity fails. What is the most likely cause?
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
✓
Overlapping CIDR blocks prevent VPC peering connectivity.
The most likely cause of connectivity failure is the overlapping CIDR blocks. VPC peering requires non-overlapping IP ranges for proper routing. Even if the peering connection is active and routes are added, the identical CIDR blocks (both 10.0.0.0/16) prevent the route tables from distinguishing the traffic destination, resulting in no connectivity. Option A is incorrect because VPC peering does not support transitive routing, but that is not the issue here. Option B is incorrect because the status would need to be 'active' for connectivity, but the problem is overlapping CIDRs. Option D is incorrect because although routes may be missing, the primary issue is the overlapping CIDRs.
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 peering connection is not set up for transitive routing.
Why it's wrong here
VPC peering is non-transitive, but that's not the issue.
- ✗
The peering connection status is 'pending-acceptance'.
Why it's wrong here
If pending, it wouldn't work, but overlapping is the core issue.
- ✓
Overlapping CIDR blocks prevent VPC peering connectivity.
Why this is correct
VPC peering does not support overlapping CIDRs.
- ✗
The route tables do not have a route to the peering connection.
Why it's wrong here
Routes are added but cannot work with overlapping CIDRs.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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