ANS-C01 Network Implementation Practice Question
Exhibit
Refer to the exhibit.
AWS CLI output:
{
"RouteTables": [
{
"Associations": [
{
"Main": true,
"RouteTableId": "rtb-12345",
"SubnetId": null
}
],
"Routes": [
{
"DestinationCidrBlock": "10.0.0.0/16",
"GatewayId": "local",
"Origin": "CreateRouteTable",
"State": "active"
},
{
"DestinationCidrBlock": "0.0.0.0/0",
"NatGatewayId": "nat-67890",
"Origin": "CreateRoute",
"State": "active"
}
],
"RouteTableId": "rtb-12345",
"VpcId": "vpc-abcde"
}
]
}Refer to the exhibit. A subnet is created in VPC vpc-abcde but no explicit route table association is set. What is the default route for internet-bound traffic from this subnet?
⚠ Common exam trap
The ANS-C01 exam often tests the misconception that a subnet without an explicit route table association has no routing, when in fact it inherits the VPC's main route table, which may include a default route to a NAT Gateway or Internet Gateway.
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
✓
Traffic goes through the NAT Gateway nat-67890.
When a subnet is created in a VPC without an explicit route table association, it is implicitly associated with the VPC's main route table. The main route table in this scenario includes a default route (0.0.0.0/0) pointing to NAT Gateway nat-67890, so internet-bound traffic from this subnet is directed through the NAT Gateway. This allows instances in private subnets to initiate outbound internet connections while preventing inbound traffic from the internet.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Traffic is dropped because no explicit association is set.
Why it's wrong here
The subnet uses the main route table by default.
- ✗
Traffic goes through the Internet Gateway.
Why it's wrong here
No Internet Gateway is associated.
- ✓
Traffic goes through the NAT Gateway nat-67890.
Why this is correct
The main route table has a route to the NAT Gateway.
- ✗
Traffic is dropped because no Internet Gateway is present.
Why it's wrong here
The main route table has a NAT Gateway route.
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Written by Johnson Ajibi, MSc IT Security
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