ANS-C01 Network Implementation Practice Question
A company has a Direct Connect connection with a private VIF to a Direct Connect gateway. The VIF is associated with a Direct Connect gateway that has a virtual private gateway (VGW) attachment to a VPC. The on-premises network is advertising a route to 10.0.0.0/16. However, the VPC cannot reach on-premises resources. The VPC has a route table with a route to 10.0.0.0/16 pointing to the VGW. What is the MOST likely cause?
⚠ Common exam trap
The ANS-C01 exam often tests the understanding that a static route to the VGW is sufficient for routing, but candidates must verify that BGP is properly advertising on-premises routes to the Direct Connect gateway; otherwise, the VGW will not know how to reach on-premises, even with a static VPC route.
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
✓
The on-premises router is not using BGP to advertise routes
The VPC route table already contains a static route to 10.0.0.0/16 pointing to the VGW, so route propagation is not required for this specific destination. However, for the VGW to forward traffic to on-premises, it must have learned the on-premises route via BGP from the Direct Connect gateway. If the on-premises router is not using BGP to advertise the 10.0.0.0/16 route, the Direct Connect gateway and therefore the VGW will not have a route to that prefix, causing traffic from the VPC to be dropped. Enabling route propagation on the VPC route table would not help because the route is already statically defined. Therefore, the most likely cause is that the on-premises router is not using BGP to advertise routes.
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 VPC route table does not have route propagation enabled for the virtual private gateway
Why it's wrong here
Without propagation, the VPC does not learn on-premises routes.
- ✓
The on-premises router is not using BGP to advertise routes
Why this is correct
BGP is required for private VIF, but the VGW may still receive routes.
- ✗
The security group on the VPC instances is blocking inbound traffic
Why it's wrong here
Security groups are stateful and do not affect routing.
- ✗
The Direct Connect gateway does not support the prefix 10.0.0.0/16
Why it's wrong here
Direct Connect gateway supports any prefix.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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