Windows instance unreachable after instance type change

Question

Hello,

Today I attempted an instance type change on a Windows machine from m5.4xlarge to c6a.4xlarge resulting in Instance reachability check failed. I've tried rebooting, stopping, and starting the instance, but the outcome was the same: no connectivity.

Are there any networking differences between the 2 instance types that would require driver installation? I'm asking about the network, as the instance screenshot displayed no connectivity on the network adapter and the remote desktop connection was not working either.

Answer

Your AMI may have an outdated network driver.

Do update your ENA network driver as per [What do I need to do before migrating my EC2 instance to a sixth generation instance to make sure that I get maximum network performance?](https://aws.amazon.com/premiumsupport/knowledge-center/migrate-to-gen6-ec2-instance/)

For Windows installation instructions, refer to [Enable enhanced networking with the Elastic Network Adapter (ENA) on Windows instances](https://docs.aws.amazon.com/AWSEC2/latest/WindowsGuide/enhanced-networking-ena.html#enable-enhanced-networking-ena-WIN)

Answer

Based on the article you have posted, my understanding is that c6a.4xlarge is not ENA compatible and m5.4xlarge is.

Is this the case? I am a bit confused about the terminology here.

Answer

Yes, you are correct. There are differences esp with the network adapator.

Please see https://docs.aws.amazon.com/AWSEC2/latest/WindowsGuide/resize-limitations.html for Compatibility

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Windows instance unreachable after instance type change

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