AWS Certified Advanced Networking – Specialty (ANS-C00) — Question 310

You work for a company that has several instances running with automatically assigned public IPs. You performed an upgrade that required you to restart the instances from the console and your DNS records don't work anymore. What happened?

Answer options

• A. Your network interfaces need to be reinitialized
• B. You need to restart Route 53
• C. Restarting too many instances at once overloads the system
• D. The instances changed their public IP addresses on restart

Correct answer: D

Explanation

When instances with automatically assigned public IP addresses are stopped and started, their public IPs are released back to the pool and new ones are assigned, which breaks any existing DNS records pointing to the old IPs. To prevent this issue, Elastic IP addresses should be used to ensure the public IPs remain static across restarts. Other options, such as restarting Route 53 or reinitializing network interfaces, are incorrect because Route 53 does not require restarts and network interfaces handle this automatically.