EC2 instance network connection

Question

I use EC2 instance services in AWS,
today I faced an issue in my network instance, my instance network in poor,
and RDP connection is slow and it's services in this instance interrupts, 
in same time, I test another instance already running in my console and it's work fine and it's network in strong,
why first instance has poor network connection in some time ?

re:Post Agent · Answer

There could be several reasons why one EC2 instance is experiencing poor network connectivity while another is working fine. Here are some potential causes and troubleshooting steps:

1. Instance type changes: If you recently changed the instance type, it might have affected the network adapter driver, leading to connectivity issues. Ensure you have the correct network adapter driver installed for your current instance type.

2. ENA (Elastic Network Adapter) issues: Check if your instance is using ENA and if there are any problems with it. You may need to update the ENA driver to the latest version or adjust some settings.

3. Network buffer size: The network adapter receive buffer size might need adjustment. Increasing it to 8192 using a PowerShell command can sometimes improve network performance.

4. Resource allocation: Check the CPU usage levels using Resource Monitor. For larger instance types, you might need to configure RSS (Receive Side Scaling) to exclude CPU 0.

5. Instance status: Verify that the instance has passed all status checks and is in a "running" state.

6. Security group and network ACL settings: Ensure that your security group rules and network ACL settings allow the necessary inbound and outbound traffic.

7. VPC and subnet configuration: Check that your VPC and subnet are correctly configured with proper routing to the internet gateway.

8. Instance location and network congestion: The physical location of your EC2 instances within the AWS infrastructure can affect network performance. Temporary network congestion in specific availability zones might cause intermittent issues.

To resolve the issue, you can try restarting the instance, updating network drivers, adjusting network settings, or even creating and attaching a new elastic network interface to test connectivity. If the problem persists, you may need to contact AWS support for further assistance.  
**Sources**  
[Troubleshoot an RDP connection on Windows Server after EC2 change | AWS re:Post](https://repost.aws/knowledge-center/rdp-connect-ec2-instance-change)  
[Resolve issues with ENA on an EC2 instance | AWS re:Post](https://repost.aws/knowledge-center/ec2-elastic-network-adapter-issues)  
[Troubleshoot issues connecting to your Amazon EC2 Linux instance - Amazon Elastic Compute Cloud](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/TroubleshootingInstancesConnecting.html)

EC2 instance network connection

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