Will my EC2 instance lose its public IP during scheduled system-reboot maintenance?

1. No, your EC2 instance will not lose its public IP address during the scheduled system-reboot maintenance. During a system-reboot event, the instance retains its IP address and DNS name, even though it moves to a new host. This is different from stopping and starting an instance, which would typically result in a new public IP being assigned.

2. The duration of a system-reboot is generally longer than a normal reboot because it involves moving the instance to a new host. While AWS doesn't specify an exact duration, they provide a maintenance window (in your case, a 2-hour window from 2025-06-16 02:00:00 UTC to 2025-06-16 04:00:00 UTC). The actual downtime for your instance will likely be shorter than this entire window, but it will be longer than a typical instance reboot.

During this maintenance:

• Your instance will be unavailable for a period within the specified window.
• The instance will be moved to a new host.
• After the reboot, the scheduled event will be cleared, and the event description will be updated.
• Any data on local instance store volumes will be preserved.
• You'll be able to use your instance again after it has fully booted.

It's important to note that while the public IP address will not change due to this system-reboot, it's generally a good practice to use Elastic IP addresses for instances that require a static public IP address, as this ensures the IP remains consistent even if you need to stop and start the instance in the future.
Sources
Manage Amazon EC2 instances scheduled for reboot - Amazon Elastic Compute Cloud
Amazon EC2 instance IP addressing - Amazon Elastic Compute Cloud

Great questions — here’s some clarity on both points regarding the scheduled system-reboot maintenance:

Public IP Address Change Since your EC2 instance does not have an Elastic IP (EIP) associated with it and is using a public IP assigned from the AWS pool, a system-reboot can cause the public IP address to change. To retain the same public IP through reboots, you need to associate an Elastic IP with the instance. If maintaining a consistent IP is critical for your application, it's strongly recommended to allocate and associate an EIP before the maintenance window. Reboot Duration A system-reboot during scheduled maintenance is typically similar in duration to a manual reboot — generally a few minutes, depending on instance type and load. However, AWS reserves a 2-hour window (in your case, 02:00–04:00 UTC) to allow flexibility across many instances and regions. Your instance will be unavailable only during the actual reboot and not for the entire window (unless something unexpected occurs). Tip: You can monitor the reboot through CloudWatch logs or EC2 system logs to determine exactly when your instance goes down and comes back up.

Let me know if you need help assigning an Elastic IP or preparing for any side effects of the reboot.

Hope this helps!