ANS-C01 Question 353
Single answerYour organization uses a VPC with a private subnet containing 200 EC2 instances. The subnet routes outbound internet traffic to a NAT Gateway. Recently, some instances have been unable to connect to external services intermittently. Upon investigation, you find that the issue coincides with a large-scale data transfer from other instances in the same subnet. What is the most likely cause of this issue, and how can it be resolved?
- A
The NAT Gateway has reached its bandwidth limit. Increase the NAT Gateway's bandwidth by attaching additional Elastic IPs.
- B
The NAT Gateway has reached its bandwidth limit. Scale horizontally by deploying additional NAT Gateways in the same Availability Zone.
- C
The route table associated with the subnet has exceeded its limit for the number of routes. Add a new route table and associate it with the subnet.
- D
The Elastic IP attached to the NAT Gateway has a quota limit. Request a service limit increase for Elastic IPs in your region.
Show answer and explanation
Correct answer: B
Explanation
NAT Gateways have a fixed bandwidth limit, which can cause connectivity issues under heavy traffic. To mitigate this, you can deploy multiple NAT Gateways in the same Availability Zone and distribute traffic across them. This ensures that the instances in your private subnet have sufficient outbound internet bandwidth.
- A. Incorrect.
NAT Gateways do not allow bandwidth increases through Elastic IPs. Bandwidth limits are tied to the NAT Gateway itself, not its IP addresses.
- B. Correct.
NAT Gateways have a fixed bandwidth limit (up to 45 Gbps as of October 2023). To handle increased traffic, additional NAT Gateways should be deployed, and traffic should be distributed across them.
- C. Incorrect.
Route table limits typically affect the number of routes allowed, not bandwidth or connectivity issues. This is unlikely to be the root cause in this scenario.
- D. Incorrect.
Elastic IP quotas are unrelated to the bandwidth limits of a NAT Gateway. Elastic IPs are used for providing static public IP addresses, not for increasing bandwidth.