Using AWS EC2, the BIG_IP VPN client does not communicate with the client server.

Based on the information provided, it appears you're experiencing intermittent connectivity issues with your BIG-IP VPN client connecting to an AWS EC2 instance. While the specific cause isn't explicitly mentioned in the available AWS Client VPN troubleshooting documentation, there are several potential areas to investigate:

1. Network and Firewall Configuration: Ensure that the firewall rules on both your local machine and the AWS EC2 instance are not blocking inbound or outbound TCP or UDP traffic on ports 443 or 1194, which are commonly used for VPN connections.

2. Certificate and Authentication: Verify that the client configuration file contains the correct client key and certificate. An expired or invalid certificate can cause connection issues.

3. Client Revocation List (CRL): Check if the CRL is still valid. An expired CRL can prevent successful connections.

4. DNS Resolution: Ensure that the Client VPN endpoint's DNS name is resolving correctly to the appropriate IP address.

5. EC2 Instance Health: Verify that the EC2 instance hosting the VPN server is running and healthy. Intermittent issues could be related to instance performance or availability.

6. Network Path: Check for any network issues between your local network and AWS, as intermittent connectivity could be caused by routing or internet service provider problems.

7. VPN Client Software: Ensure you're using the latest version of the BIG-IP VPN client and that it's compatible with the AWS EC2 setup.

To troubleshoot further, you may need to:

• Review the VPN client logs for specific error messages
• Check the EC2 instance logs for any connection attempts or errors
• Verify the AWS Client VPN endpoint configuration
• Test connectivity using a different VPN client to isolate whether the issue is specific to the BIG-IP client

If the issue persists, you may need to involve your AWS Client VPN administrator to investigate the endpoint configuration and EC2 instance settings in more detail.
Sources
Troubleshooting common AWS Client VPN problems - AWS Client VPN
Troubleshooting AWS Client VPN - AWS Client VPN
Troubleshooting AWS Client VPN connections - AWS Client VPN