Client VPN connection problems to instances with Elastic IPs after upgrading to AWS VPN Client v5.0.0

Thank you for bringing this issue to our attention, Joni. The problem you're experiencing with the AWS VPN Client v5.0.0 and connections to EC2 instances with Elastic IPs is concerning. While I don't have specific information about this particular version causing issues with Elastic IPs, I can provide some general troubleshooting steps and insights that might help:

1. First, it's important to verify that your Client VPN endpoint configuration is correct. Check that the authorization rules for your VPC's CIDR range are properly set up in the Client VPN endpoint configuration.

2. Ensure that the DNS settings for your Client VPN endpoint are correctly configured. If you're using a private hosted zone, make sure that the Client VPN endpoint is set to use the appropriate DNS servers that can resolve your private hostnames.

3. Check the route tables associated with the subnets where your EC2 instances are located. Verify that there are correct route entries for both the VPC CIDR and for internet access (if required).

4. If you're trying to access instances with Elastic IPs, ensure that the security groups and network ACLs allow the necessary inbound traffic from the Client VPN CIDR range.

5. Review the Client VPN logs for any specific error messages that might provide more insight into the connection issues. You can send these diagnostic logs to AWS Support for further assistance.

6. Since downgrading to v4.1.0 resolved the issue, it's possible that there might be a bug in v5.0.0. It would be helpful to report this to AWS Support, providing them with the details of your setup and the problems you encountered.

7. In the meantime, if v4.1.0 is working correctly for you, it might be best to continue using that version until the issue with v5.0.0 is resolved.

If the problem persists or you need further assistance, I recommend contacting AWS Support directly. They can provide more specific guidance based on your exact configuration and may be able to investigate if this is a known issue with the latest client version.

Sources
Troubleshooting Intermittent Connection Loss Between AWS VPN Client and EC2 Instance in a VPC | AWS re:Post
Troubleshooting common AWS Client VPN problems - AWS Client VPN
Troubleshooting AWS Client VPN: Clients can't access a peered VPC, Amazon S3, or the internet - AWS Client VPN